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Objective: The aims of this study were to investigate biochemical and genetic tests and treatment plans of newborns referred to our center with inherited metabolic disorders screened in Türkiye National Newborn Screening Program (NNSP). Material and Methods: The medical records of babies referred by the NNSP between January 2019 and November 2023 were scanned retrospectively. Plasma biotinidase activity and the biotinidase gene (BTD) analysis results for suspected biotinidase deficiency (BD), the plasma phenylalanine and phenylalanine hydroxylase gene (PAH) analysis for a suspicion of phenylketonuria (PKU) were documented with treatment information. Results: A total of 143 babies, 78 (54.5%) with suspected BD and 65 (45.5%) with suspected PKU were included. A PAH gene analysis was performed on 23 (35.4%) of those had high plasma phenylalanine levels, among which 86.9% were identified with the biallelic variant. Five patients were started on sapropterin-diet combined therapy, three on diet therapy and one on sapropterin therapy. In the first serum biotinidase activity measurement of babies referred with suspected BD, a heterozygous deficiency was detected in 48.7%, partial deficiency in 39.7% and profound deficiency in 10.3%. A BTD gene analysis was performed on 79.5% of those with suspected BD, and biallelic variants were detected in 50%. Forty-six patients (59.0%) underwent biotin treatment. Conclusion: In our study, approximately one-third of the babies referred from NNSP over the five-year course of the study had biallelic variants of the relevant disease. Our research is one of the few studies on NNSP in our country and presents the diagnosis and treatment process of PKU and BD. [ABSTRACT FROM AUTHOR]

Phenylketonuria (PKU) results from a deficiency in phenylalanine hydroxylase, catalyzing the conversion of phenylalanine (Phe) to tyrosine. Premenstrual syndrome (PMS) consists of physical, behavioral, and emotional symptoms occurring during the last week of luteal phase. The aim of the study was to determine the incidence of PMS, and document menstrual cycle characteristics of PKU patients to reveal the relationship with blood Phe levels. The study was conducted on 74 patients with a mean age of 21.7 ± 5.4 years. The mean age at menarche was 12.7 ± 1.3 years and 82.4 % had regular menstrual cycles. The periods of most patients (47.2 %) lasted 4–5 days. Menstrual cycles of 21–28 days were reported by 73 %, less than 21 days by 8 %, and more than 28 days by 19 % of women. Menorrhagia and dysmenorrhea was observed in 6.7 % and 71.6 % respectively. Adherence to diet was lost in 7 patients during the menstrual period. No significant relationship was found between Phe levels and PMS symptoms (p > 0.05). According to PMSS subscales, 52.7 % of patients with PKU had depressive feelings, 16.2 % anxiety, 55.4 % fatigue, 52.7 % irritability, 28.3 % depressive thoughts, 39.1 % pain, 59.4 % changes in appetite, 28.3 % changes in sleeping habits and 43.2 % had swelling. The findings of the study revealed that PMS prevalence was 39.1 % among PKU women. Awareness about this syndrome, will improve the quality of life in women with PKU by evaluating and taking measures for PMS. Synopsis: Evaluating menstrual cycle characteristics and premenstrual syndrome in phenylketonuria patients provides valuable insights for enhancing their overall health profile and personalizing treatment and management plans.

Abstract Background Phenylketonuria (PKU) is an inborn error of phenylalanine (Phe) metabolism that, if untreated, causes Phe accumulation in the brain leading to neurophysiologic alterations and poor outcomes. Lifelong management centers on dietary Phe restriction, yet long-term complete metabolic control is unachievable for many adults. High blood Phe levels or chronic Phe and intact protein restriction in the diet may lead to somatic comorbidities. A systematic literature review was conducted to evaluate somatic comorbidities experienced by adults with PKU. Methods Clinical and observational studies reporting somatic comorbidities experienced by individuals with PKU aged ≥ 16 years (or classified as adults) evaluating a Phe-restricted diet with or without pharmacologic therapy versus no therapeutic intervention (including healthy controls), or pharmacologic therapy versus a Phe-restricted diet alone, were identified. PubMed® was searched (February 1, 2022 and updated November 1, 2023), using a pre-defined search strategy, followed by two-stage screening and data extraction. Included studies were grouped by PKU population comparison. Results 1185 records were screened; 51 studies across 12,602 individuals were extracted. Bone-related abnormalities were the most reported outcome (n = 21); several outcome measures were used. Original study groupings included: Phe-restricted diet versus healthy controls or reference values (n = 40); treatment-adherent versus those non-adherent (n = 12). Additional groups added as part of a protocol amendment included: different Phe-restricted diets (n = 4); severe versus less severe disease (n = 5). Vote counting indicated a higher burden of ≥ 1 comorbidity (or outcome measure) for the Phe-restricted diet group by 37 of 38 studies included in the analysis of Phe-restricted diet versus healthy controls; higher burden in healthy controls was reported in 12 studies. Vote counting was similar between those treatment adherent (n = 7) versus non-adherent (n = 10). Conclusions Adults with PKU have a higher comorbidity burden than a non-PKU population. More robust studies are needed to better understand the relationship between effective metabolic control and comorbidity burden, using consistent outcome measures. This SLR was supported by BioMarin Pharmaceutical Inc., Novato, CA, and is registered with the Research Registry (reviewregistry1476).

Background: Phenylketonuria (PKU) is an inborn error of phenylalanine (Phe) metabolism that, if untreated, causes Phe accumulation in the brain leading to neurophysiologic alterations and poor outcomes. Lifelong management centers on dietary Phe restriction, yet long-term complete metabolic control is unachievable for many adults. High blood Phe levels or chronic Phe and intact protein restriction in the diet may lead to somatic comorbidities. A systematic literature review was conducted to evaluate somatic comorbidities experienced by adults with PKU. Methods: Clinical and observational studies reporting somatic comorbidities experienced by individuals with PKU aged ≥ 16 years (or classified as adults) evaluating a Phe-restricted diet with or without pharmacologic therapy versus no therapeutic intervention (including healthy controls), or pharmacologic therapy versus a Phe-restricted diet alone, were identified. PubMed® was searched (February 1, 2022 and updated November 1, 2023), using a pre-defined search strategy, followed by two-stage screening and data extraction. Included studies were grouped by PKU population comparison. Results: 1185 records were screened; 51 studies across 12,602 individuals were extracted. Bone-related abnormalities were the most reported outcome (n = 21); several outcome measures were used. Original study groupings included: Phe-restricted diet versus healthy controls or reference values (n = 40); treatment-adherent versus those non-adherent (n = 12). Additional groups added as part of a protocol amendment included: different Phe-restricted diets (n = 4); severe versus less severe disease (n = 5). Vote counting indicated a higher burden of ≥ 1 comorbidity (or outcome measure) for the Phe-restricted diet group by 37 of 38 studies included in the analysis of Phe-restricted diet versus healthy controls; higher burden in healthy controls was reported in 12 studies. Vote counting was similar between those treatment adherent (n = 7) versus non-adherent (n = 10). Conclusions: Adults with PKU have a higher comorbidity burden than a non-PKU population. More robust studies are needed to better understand the relationship between effective metabolic control and comorbidity burden, using consistent outcome measures. This SLR was supported by BioMarin Pharmaceutical Inc., Novato, CA, and is registered with the Research Registry (reviewregistry1476). [ABSTRACT FROM AUTHOR]

Phenylalanine hydroxylase (PAH) is predominantly a hepatic enzyme that catalyzes phenylalanine (Phe) into tyrosine, which is the rate-limiting step in Phe catabolism. Biallelic variants in the PAH gene cause PAH enzyme deficiency. Phenylketonuria (PKU) is an autosomal recessive disorder that causes neurologic, behavioral, and dermatological findings. PKU could be divided clinically into three types based on the blood Phe levels: classic phenylketonuria (cPKU), mild-moderate phenylketonuria (mPKU), and mild hyperphenylalaninemia (MHP). This study aimed to determine the phenotypic and genotypic characteristics of Turkish PKU patients in the eastern region of Türkiye. Demographic characteristics, serum Phe levels, treatments, and PAH variants of 163 patients with PKU and hyperphenylalaninemia (HPA) were retrospectively evaluated. Blood Phe levels of the patients were analyzed with the high-performance liquid chromatography method. For PAH gene analysis, next-generation sequencing was performed. Of the 163 patients included in the study, 38 (23.3 %) had cPKU, 16 (9.8 %) had mPKU, and 109 (66.9 %) had MHP. Homozygous variants in the PAH gene were detected in 66 (40.5 %) of the patients, while compound heterozygous variants were detected in 97 (59.5 %) patients. Two novel and 35 recurrent variants in the PAH gene were detected. Of the two novel variants, one was missense (p.Phe351Leu) and the other was frameshift (p.Met276Cysfs*65). The most frequently detected variants were p.Thr380Met (18 %), p.Arg261Gln (16.8 %), and p.Ala300Ser (12.8 %). All patients with the homozygous c.1066-11G>A variant exhibited cPKU phenotype. The c.898G>T (p.Ala300Ser), c.1139C>T (p.Thr380Met), and c.1208C>T (p.Ala403Val) variants were statistically related to mild phenotype. On the other hand, c.592_613del (p.Tyr198Serfs*136), c.1028A>G (p.Tyr343Cys), and c.782G>A (p.Arg261Gln) variants were more frequently detected in the cPKU group. Our study, conducted with patients from the eastern region of Türkiye, demonstrates the genetic heterogeneity in the Turkish population. Simultaneously, our research contributes to genotype–phenotype correlation and expands the genotypic spectrum by identifying novel variants. [ABSTRACT FROM AUTHOR]

BackgroundAromatic compounds derived from tyrosine are important and diverse chemicals that have industrial and commercial applications. Although these aromatic compounds can be obtained by extraction from natural producers, their growth is slow, and their content is low. To overcome these problems, many of them have been chemically synthesized from petroleum-based feedstocks. However, because of the environmental burden and depleting availability of feedstock, microbial cell factories are attracting much attention as sustainable and environmentally friendly processes.ResultsTo facilitate development of microbial cell factories for producing tyrosine derivatives, we developed simple and convenient tyrosine-producing Escherichia coli platforms with a bacterial phenylalanine hydroxylase, which converted phenylalanine to tyrosine with tetrahydromonapterin as a cofactor, using a synthetic biology approach. By introducing a tetrahydrobiopterin-regeneration system, the tyrosine titer of the plasmid-based engineered strain was 4.63 g/L in a medium supplemented with 5.00 g/L phenylalanine with a test tube. The strains were successfully used to produce industrially attractive compounds, such as tyrosol with a yield of 1.58 g/L by installing a tyrosol-producing module consisting of genes encoding tyrosine decarboxylase and tyramine oxidase on a plasmid. Gene integration into E. coli chromosomes has an advantage over the use of plasmids because it increases genetic stability without antibiotic feeding to the culture media and enables more flexible pathway engineering by accepting more plasmids with artificial pathway genes. Therefore, we constructed a plasmid-free tyrosine-producing platform by integrating five modules, comprising genes encoding the phenylalanine hydroxylase and tetrahydrobiopterin-regeneration system, into the chromosome. The platform strain could produce 1.04 g/L of 3,4-dihydroxyphenylalanine, a drug medicine, by installing a gene encoding tyrosine hydroxylase and the tetrahydrobiopterin-regeneration system on a plasmid. Moreover, by installing the tyrosol-producing module, tyrosol was produced with a yield of 1.28 g/L.ConclusionsWe developed novel E. coli platforms for producing tyrosine from phenylalanine at multi-gram-per-liter levels in test-tube cultivation. The platforms allowed development and evaluation of microbial cell factories installing various designed tyrosine-derivative biosynthetic pathways at multi-grams-per-liter levels in test tubes.

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Background: There are more than 1100 different pathogenic variants in the phenylalanine hydroxylase (PAH) gene that are responsible for phenylketonuria (PKU) diseases, and the spectrum of these mutations varies in different ethnic groups. The aim of the present study was to identify the frequency of pathogenic variants in all 13 exons of the PAH gene among patients with PKU in Mazandaran and Golestan provinces in the north of Iran. Methods: Forty unrelated PKU patients from Mazandaran and Golestan provinces were enrolled in the study. Genomic DNA was extracted from leukocytes using a Qiagen DNA extraction kit and polymerase chain reaction -- restriction fragment length polymorphism (PCR-RFLP), and Sanger sequencing methods were applied to detect the variants. In the case of new variants, the InterVar online tool (PMID: 28132688) was used to classify the variants. Results: Twenty-one different pathogenic variants were observed among the 40 investigated patients. The c.106611G>A variant had the highest frequency (27.5%) in the region, and the c.168+5G>C, c.473G>A, and c.782 G>A variants were the other most frequent mutations with allelic frequencies of 7.5, 5, and 5%, respectively. Three novel pathogenic variants including c.773T>G, c.878 T>C, and c. 1245del variants were observed among the investigated patients. Conclusions: The introduction of pathogenic variants in the PAH gene in each ethnic group provides valuable data regarding the understanding of the pathogenesis of the disease and can be helpful for prenatal diagnosis programs. [ABSTRACT FROM AUTHOR]

Abstract Phenylketonuria (PKU) is an autosomal recessive inborn error of metabolism resulting from a deficiency of phenylalanine hydroxylase (PAH). If untreated by dietary restriction of phenylalanine intake, impaired postnatal cognitive development results from the neurotoxic effects of excessive phenylalanine (Phe). Signs and symptoms include severe intellectual disability and behavior problems with a high frequency of seizures and variable microcephaly. Maternal PKU syndrome refers to fetal damage resulting in congenital abnormalities when the mother has untreated PKU during pregnancy. Here, we report an intellectually normal 32‐year‐old female who presented with recurrent pregnancy loss and two neonatal deaths with congenital heart disease, microcephaly, intrauterine growth restriction, and respiratory distress. She was diagnosed with PKU through exome sequencing performed for carrier testing with a homozygous pathogenic variant in the PAH gene, c.169_171del, p.(Glu57del) that is associated with classical PKU. Consistent with the genetic finding, she had a markedly increased plasma phenylalanine concentration of 1642 μmol/L (normal

Tyrosol (4-hydroxyphenylethanol) is a phenolic compound used in the pharmaceutical and chemical industries. However, current supply methods, such as extraction from natural resources and chemical synthesis, have disadvantages from the viewpoint of cost and environmental protection. Here, we developed a tyrosol-producing Escherichia coli cell factory from a high-tyrosine-producing strain by expressing selected tyrosine decarboxylase-, tyramine oxidase (TYO)-, and medium-chain dehydrogenase/reductase (YahK)-encoding genes. The genes were controlled by the strong T7 promoter and integrated into the chromosome because of the advantages over plasmid-based systems. The strain produced a melanin-like pigment as a by-product, which is suggested to be formed from 4-hydroxyphenylacetaldehyde (a TYO product/YahK substrate). By using a culture medium containing a high concentration of glycerol, which was reported to enhance NADH supply required for YahK activity, the final titer of tyrosol reached 2.42 g/L in test tube-scale cultivation with a concomitant decrease in the amount of pigment. These results indicate that chromosomally integrated and T7 promoter-controlled gene expression system in E. coli is useful for high production of heterologous enzymes and might be applied for industrial production of useful compounds including tyrosine and tyrosol. [Display omitted] [ABSTRACT FROM AUTHOR]

Background: Phenylketonuria (PKU) is an autosomal recessive metabolic genetic disorder characterized by a mutation in the gene for the hepatic enzyme phenylalanine hydroxylase (PAH). The disease may present clinically with seizures, developmental delay, hyperactivity, autistic symptoms, blue eyes, rough and dry skin, albinism or blond hair and skin and a "musty odor" to the baby's urine and sweat. Aim of the Work: To evaluate management of phenylketonuria in infants and children. Program and methods: All patients diagnosed as phenylketonuria based on screening program, clinical and laboratory findings by measuring phenyl alanine level in the blood were retrospectively assessed through checking the files of patients at Assiut Genetic Counseling Centre and Al-Azhar Assiut University Hospital from 1st January 2016 to 28th February 2021, All files of patients were evaluated through full history taking, general and complete neurological examination and developmental assessment, serum phenyl alanine and tetrahydrobiopterin loading test was done in some cases. Intelligent Question (IQ), Electroencephalogram (EEG), Childhood Autistic Rating Scale (CARS), Attention Deficit Hyperactivity Disorder (ADHD) test and Brain Magnetic Resonance Imaging (MRI) were done in some cases. Results: In our study we estimated 400 cases retrospectively with phenylketonuria, 240 of them were found to be less than 6 months old (60%) diagnosed by screening while 160 of them ages more than 6 months (40%) diagnosed with clinical suspicion plus elevated serum phenyl alanine with mean age ± SD (1.99± 1.32) years. 204 cases were males (51%) and 196 cases were females (49%). 276 cases (69%) lived in rural areas and 124 cases (31%) lived in urban areas. 230 cases (57.5%) were offsprings of consanguineous parents. 250 cases (62.5%) had similar condition in their families. 160 cases (40%) were diagnosed by clinical presentation which included blond hair and other findings as follows: blond hair and autism in 24 cases (15%), blond hair and mental retardation in 60 cases (37.5%), blond hair and hyperactivity in 34 cases (21.25%), blond hair and seizures 29 in cases (18.125%), blond hair and bad odor urine 13 cases (8.125%). 132 cases (33%) had Phenyl alanine (Phe) level more than 1200µmol/L (classical PKU), 107 cases (26.8%) had Phe level between 900&1200µmol/L (moderate PKU) and most of them 161 cases (40.3%) had Phe level between 600&900µmol/L (mild PKU). 308 cases (77%) were compliant to dietary supplement and healthcare recommendations and 92 cases (23%) were non-compliant. Conclusion: Mild PKU was the most common form (40%) followed by the classic form (33%). Most of diagnosed cases of PKU asked for dietary supplementation and health care recommendations (77%). The development of Egyptian neonatal screening programs demonstrated how effective treatment can lead to a near normal outcome for affected individuals. [ABSTRACT FROM AUTHOR]

Phenylketonuria (PKU) or hyperphenylalaninemia is considered a paradigm for an inherited (metabolic) liver defect and is, based on murine models that replicate all human pathology, an exemplar model for experimental studies on liver gene therapy. Variants in the PAH gene that lead to hyperphenylalaninemia are never fatal (although devastating if untreated), newborn screening has been available for two generations, and dietary treatment has been considered for a long time as therapeutic and satisfactory. However, significant shortcomings of contemporary dietary treatment of PKU remain. A long list of various gene therapeutic experimental approaches using the classical model for human PKU, the homozygous enu2/2 mouse, witnesses the value of this model to develop treatment for a genetic liver defect. The list of experiments for proof of principle includes recombinant viral (AdV, AAV, and LV) and non‐viral (naked DNA or LNP‐mRNA) vector delivery methods, combined with gene addition, genome, gene or base editing, and gene insertion or replacement. In addition, a list of current and planned clinical trials for PKU gene therapy is included. This review summarizes, compares, and evaluates the various approaches for the sake of scientific understanding and efficacy testing that may eventually pave the way for safe and efficient human application. [ABSTRACT FROM AUTHOR]

Abstract Background Aromatic compounds derived from tyrosine are important and diverse chemicals that have industrial and commercial applications. Although these aromatic compounds can be obtained by extraction from natural producers, their growth is slow, and their content is low. To overcome these problems, many of them have been chemically synthesized from petroleum-based feedstocks. However, because of the environmental burden and depleting availability of feedstock, microbial cell factories are attracting much attention as sustainable and environmentally friendly processes. Results To facilitate development of microbial cell factories for producing tyrosine derivatives, we developed simple and convenient tyrosine-producing Escherichia coli platforms with a bacterial phenylalanine hydroxylase, which converted phenylalanine to tyrosine with tetrahydromonapterin as a cofactor, using a synthetic biology approach. By introducing a tetrahydrobiopterin-regeneration system, the tyrosine titer of the plasmid-based engineered strain was 4.63 g/L in a medium supplemented with 5.00 g/L phenylalanine with a test tube. The strains were successfully used to produce industrially attractive compounds, such as tyrosol with a yield of 1.58 g/L by installing a tyrosol-producing module consisting of genes encoding tyrosine decarboxylase and tyramine oxidase on a plasmid. Gene integration into E. coli chromosomes has an advantage over the use of plasmids because it increases genetic stability without antibiotic feeding to the culture media and enables more flexible pathway engineering by accepting more plasmids with artificial pathway genes. Therefore, we constructed a plasmid-free tyrosine-producing platform by integrating five modules, comprising genes encoding the phenylalanine hydroxylase and tetrahydrobiopterin-regeneration system, into the chromosome. The platform strain could produce 1.04 g/L of 3,4-dihydroxyphenylalanine, a drug medicine, by installing a gene encoding tyrosine hydroxylase and the tetrahydrobiopterin-regeneration system on a plasmid. Moreover, by installing the tyrosol-producing module, tyrosol was produced with a yield of 1.28 g/L. Conclusions We developed novel E. coli platforms for producing tyrosine from phenylalanine at multi-gram-per-liter levels in test-tube cultivation. The platforms allowed development and evaluation of microbial cell factories installing various designed tyrosine-derivative biosynthetic pathways at multi-grams-per-liter levels in test tubes.

The cornerstone treatment of hyperphenylalaninemia (HPA) and phenylketonuria (PKU) is a lifelong low-protein diet with phenylalanine (Phe) free L-amino acid supplements. However, the PKU diet has significant shortcomings, and there is a clinically unmet need for new therapeutics to improve patient outcomes. CDX-6114 is a modified phenylalanine ammonia-lyase (PAL) enzyme obtained by a mutation in the Anabaena variabilis PAL sequence. CodeEvolver® protein engineering technology has been applied to improve the degradation resistance of the enzyme. In our first phase I trial, 19 patients were given a single oral dose of CDX-6114 at 7.5 g, 2.5 g, 0.7 g, or placebo in a cross-over design. After an overnight fast, patients received a standardised breakfast of 20 g of protein, thus exceeding the dietary recommendations for a single meal in patients with PKU. Plasma levels of Phe and cinnamic acid (CA) were measured over a 5-h period following CDX-6114 dosing. During the development of CDX-6114, a stability assessment using reverse-phase high-performance liquid chromatography (HPLC) assay revealed two peaks. The second peak was identified as CA. It was not previously known that as part of the mechanism of action, the CA remained associated with the protein following the conversion of Phe. Thus, recalculating the historical PAL enzyme amounts in CDX-6114 bulk substance was necessary. An updated extinction coefficient was achieved by applying a correction factor of 0.771 to previously reported doses. Postprandial plasma levels of Phe increased in all dose cohorts over time between 10% and 30% from baseline, although the actual peak of Phe levels was not achieved within the 5-h observation. When accounting for the interquartile ranges, these concentrations were similar to the placebo. As plasma levels of Phe were no longer a reliable marker for pharmacodynamics, the consistently detectable amount of CA seen in all patients who received CDX-6114 provided proof of the enzymatic activity of CDX-6114 in metabolising gastrointestinal Phe. Peak levels of CA were seen shortly after CDX-6114 intake, with a rapid decline, and remained low compared with the plasma Phe levels. This pattern indicates a short half-life, possibly due to the liquid formulation or the inability to withstand the lower pH in the human stomach compared with animal models in earlier studies. This was the first trial in patients with PKU to establish the safety and tolerability of CDX-6114. A single dose of CDX-6114 was safe and well tolerated, with no serious adverse events or presence of anti-drug antibodies detected. Efficacy will be explored in future trials using an optimised formulation.

To date more than 1000 different variants in the PAH gene have been identified in patients with phenylketonuria (PKU). In Iran, several studies have been performed to investigate the genetics bases of the PKU in different parts of the country. In this study, we have analysed and present an update of the mutational landscape of the PAH gene as well as the population genetics and frequencies of detected variants for each cohort. Published articles on PKU mutations in Iran were identified through a comprehensive PubMed, Google Scholar, Web of Science (ISI), SCOPUS, Elsevier, Wiley Online Library and SID literature search using the terms: "phenylketonuria", "hyperphenylalaninemia", and "PKU" in combination with "Iran", "Iranian population", "mutation analysis", and "Molecular genetics". Among the literature‐related to genetics of PKU, 18 studies were on the PKU mutations. According to these studies, in different populations of Iran 1497 patients were included for mutation detection that resulted in detection of 129 different mutations. Results of genetic analysis of the different cohorts of Iranian PKU patients show that the most prevalent mutation in Iran is the pathogenic splice variant c.1066‐11G > A, occurring in 19.54% of alleles in the cohort. Four other common mutations were p.Arg261Gln, p.Pro281Leu, c.168 + 5G > C and p.Arg243Ter (8.18%, 6.45%, 5.88% and 3.7%, respectively). One notable feature of the studied populations is its high rate of consanguineous marriages. Considering this feature, determining the prevalent PKU mutations could be advantageous for designing screening and diagnostic panels in Iran. [ABSTRACT FROM AUTHOR]

Background and aims: Phenylketonuria (PKU) is an autosomal recessive disorder of phenylalanine (Phe) metabolism. Mutations in the phenylalanine hydroxylase (PAH) gene are the main reason for the incidence of PKU. To date, more than 1180 variants have been detected in the PAH gene. Given that the distribution pattern of mutations in the PAH gene is specific to each population, the present study was conducted to detect exon 4 mutations and adjacent flanking regions of the PAH gene in northern Iran. Methods: This is a descriptive cross-sectional study, in which 24 unrelated PKU patients in Taleghani Hospital in Gorgan were enrolled for a one-year period. After extraction of genomic DNA from leukocytes, identification of exon 4 mutations and adjacent flanking regions was performed using polymerase chain reaction (PCR) and sequencing techniques. Results: In this study, IVS4+1G>A mutation was detected in one allele (2.08%) among 48 alleles. Moreover, IVS4+47C>T and IVS3-22C>T polymorphisms were observed in 12 alleles (25%) and eight alleles (16.7%), respectively. Conclusion: In the present study, IVS4+1G>A mutation was only found in 2% of chromosomes. Hence, different mutations are responsible for PKU disease in the north of Iran, and further studies are recommended to identify all mutations in the PAH gene in the region.

Parenteral nutrition, received by many patients with intestinal failure, can induce hepatobiliary complications, which is termed as parenteral nutrition‐associated liver disease (PNALD). The spectrum of PNALD ranges from cholestasis and steatosis to fibrosis and cirrhosis. Although many factors contribute to the pathogenesis of PNALD, the underlying mechanisms remain unclear. In this study, we performed targeted metabolomics to characterize the metabolomic profile in neonatal piglets receiving total parenteral nutrition (TPN) or enteral nutrition (EN) for 1 or 2 weeks. Overall, the metabolomic signature of TPN groups differed from EN groups at both time points. Among the 20 acylcarnitines identified, a majority of them were significantly reduced in TPN groups. KEGG pathway analysis showed that phenylalanine metabolism‐associated pathways were dysregulated accompanied by more progressive liver steatosis associated with TPN. Next, we evaluated phenylalanine catabolism and its association with fatty acid oxidation in piglets and rats with PNALD. We showed that the hepatic expression of phenylalanine‐degrading enzyme phenylalanine hydroxylase (PAH) was reduced and systemic phenylalanine levels were increased in both animal models of PNALD. Moreover, carnitine palmitoyltransferase 1A, a central regulator of fatty acid oxidation, was downregulated and its expression was negatively correlated with phenylalanine levels in TPN‐fed animals. To explore the effects of phenylalanine accumulation on lipid metabolism, we treated HepG2 cells with phenylalanine co‐cultured with sodium palmitate or soybean oil emulsion to induce lipid accumulation. We found that phenylalanine treatment exacerbated lipid accumulation by inhibiting fatty acid oxidation without affecting fatty acid synthesis. In summary, our findings establish a pathogenic role of increased phenylalanine levels in driving liver steatosis, linking dysregulation of phenylalanine catabolism with lipid accumulation in the context of PNALD. [ABSTRACT FROM AUTHOR]

Phenylalanine hydroxylase (PAH) is an iron enzyme catalyzing the oxidation of l-Phe to l-Tyr during phenylalanine catabolism. Dysfunction of PAH leads to the debilitating condition phenylketonuria (PKU), which prompted research into the structure and function of PAH over the last 50 years. Despite intensive study, there is no consensus on the atomistic details of the mechanism of O2 binding and splitting by wild-type (WT) PAH and how it varies with PKU-inducing mutations, Arg158Gln and Glu280Lys. We studied structures involved in a proposed mechanism for the WT and mutants using extensive mixed quantum-classical molecular dynamics simulations. Simulations reveal a previously unobserved dynamic coupling between the active site and the mutation sites, suggesting how they can affect the catalytic performance of PAH. Furthermore, the effect of the coupling on the PAH structure agrees with and expands our understanding of the experimentally observed differences in activity between the WT and mutants.

Abstract This review discusses the epidemiology, pathophysiology, genetic etiology, and management of phenylketonuria (PKU). PKU, an autosomal recessive disease, is an inborn error of phenylalanine (Phe) metabolism caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene. The prevalence of PKU varies widely among ethnicities and geographic regions, affecting approximately 1 in 24,000 individuals worldwide. Deficiency in the PAH enzyme or, in rare cases, the cofactor tetrahydrobiopterin results in high blood Phe concentrations, causing brain dysfunction. Untreated PKU, also known as PAH deficiency, results in severe and irreversible intellectual disability, epilepsy, behavioral disorders, and clinical features such as acquired microcephaly, seizures, psychological signs, and generalized hypopigmentation of skin (including hair and eyes). Severe phenotypes are classic PKU, and less severe forms of PAH deficiency are moderate PKU, mild PKU, mild hyperphenylalaninaemia (HPA), or benign HPA. Early diagnosis and intervention must start shortly after birth to prevent major cognitive and neurological effects. Dietary treatment, including natural protein restriction and Phe-free supplements, must be used to maintain blood Phe concentrations of 120–360 μmol/L throughout the life span. Additional treatments include the casein glycomacropeptide (GMP), which contains very limited aromatic amino acids and may improve immunological function, and large neutral amino acid (LNAA) supplementation to prevent plasma Phe transport into the brain. The synthetic BH4 analog, sapropterin hydrochloride (i.e., Kuvan®, BioMarin), is another potential treatment that activates residual PAH, thus decreasing Phe concentrations in the blood of PKU patients. Moreover, daily subcutaneous injection of pegylated Phe ammonia-lyase (i.e., pegvaliase; PALYNZIQ®, BioMarin) has promised gene therapy in recent clinical trials, and mRNA approaches are also being studied.

Abstract Background Metazoan guts are in permanent contact with microbial communities. However, the host mechanisms that have developed to manage the dynamic changes of these microorganisms and maintain homeostasis remain largely unknown. Results Serotonin (5-hydroxytryptamine [5-HT]) was found to modulate gut microbiome homeostasis via regulation of a dual oxidase (Duox) gene expression in both Bactrocera dorsalis and Aedes aegypti. The knockdown of the peripheral 5-HT biosynthetic gene phenylalanine hydroxylase (TPH) increased the expression of Duox and the activity of reactive oxygen species, leading to a decrease in the gut microbiome load. Moreover, the TPH knockdown reduced the relative abundance of the bacterial genera Serratia and Providencia, including the opportunistic pathogens, S. marcescens and P. alcalifaciens in B. dorsalis. Treatment with 5-hydroxytryptophan, a precursor of 5-HT synthesis, fully rescued the TPH knockdown-induced phenotype. Conclusions The findings reveal the important contribution of 5-HT in regulating gut homeostasis, providing new insights into gut–microbe interactions in metazoans.

Background and aims: Phenylketonuria (PKU) is an autosomal recessive disorder of phenylalanine (Phe) metabolism. Mutations in the phenylalanine hydroxylase (PAH) gene are the main reason for the incidence of PKU. To date, more than 1180 variants have been detected in the PAH gene. Given that the distribution pattern of mutations in the PAH gene is specific to each population, the present study was conducted to detect exon 4 mutations and adjacent flanking regions of the PAH gene in northern Iran. Methods: This is a descriptive cross-sectional study, in which 24 unrelated PKU patients in Taleghani Hospital in Gorgan were enrolled for a one-year period. After extraction of genomic DNA from leukocytes, identification of exon 4 mutations and adjacent flanking regions was performed using polymerase chain reaction (PCR) and sequencing techniques. Results: In this study, IVS4+1G>A mutation was detected in one allele (2.08%) among 48 alleles. Moreover, IVS4+47C>T and IVS3-22C>T polymorphisms were observed in 12 alleles (25%) and eight alleles (16.7%), respectively. Conclusion: In the present study, IVS4+1G>A mutation was only found in 2% of chromosomes. Hence, different mutations are responsible for PKU disease in the north of Iran, and further studies are recommended to identify all mutations in the PAH gene in the region. [ABSTRACT FROM AUTHOR]

Sudipt Kumar Dalei, Nidhi Adlakha Regional Center for Biotechnology, NCR Biotech Science Cluster, Faridabad, Haryana, IndiaCorrespondence: Nidhi Adlakha Email nidhi.adlakha@rcb.res.inAbstract: In the category of rare inherited genetic disorders, phenylketonuria is a prominent example. Here, the defective phenylalanine hydroxylase enzyme fails to catalyze conversion of phenylalanine to tyrosine. This leads to not only excess deposition of phenylalanine leading to phenylalanine toxicity but also precludes the production of important glutamatergic and cholinergic neurotransmitters, leading to epileptic disorders, microcephaly, low intelligence quotient etc. For long, specialized food products are considered as preferred solution to prevent disease outcome. Different medical diets are developed for managing phenylketonuria includes amino acid mixtures, protein hydrolysates, cofactor-based therapy, large neutral amino acids and glycomacropeptides. However, despite the advent of alternate forms of diet products, the central form of treatment has still been free amino acid mixture. The formulated diet is by and large expensive and in-depth evaluation of several factors which contribute to the expense of medicated diet is requisite to create effective yet affordable avenues for management of disease. For this, we have discussed the role of various factors involved in increasing price of medicated diet and presented possible solutions to it. We have also extensively reviewed prevalence of disease, commercial diet for PKU patients, and their associated limitations. Overall, this is the first attempt to present a holistic view of balance between the overall impact of diet associated therapy and weighing it against the associated finances incurred.Keywords: phenylalanine hydroxylase, phenylketonuria, cofactor, large neutral amino acids, glycomacropeptides, protein engineering, turnover number, specificity

Phenylketonuria (PKU) is a rare genetic disease that causes brain toxicity due to the inability of the body to convert dietary phenylalanine to tyrosine by the action of phenylalanine hydroxylase. The only treatment for PKU so far is lifelong dietary intervention to ensure normal human growth and neurodevelopment. However, in adults, low long-term adherence to this type of dietary intervention has been observed. Given the important role of the intestinal microbiota in the process of digestion and disease prevention, probiotics could be a therapeutic strategy to help degrade dietary phenylalanine, reducing its levels before ingestion. Genetically modified probiotics designed as live biotherapeutic agents for the treatment of specific diseases are sophisticated alternative therapeutic strategies. In this review, the focus is on demonstrating what has been elucidated so far about the use of next-generation probiotics as a therapeutic strategy in the treatment of individuals with PKU. The results described in the literature are encouraging and use genetically modified engineered probiotics showing efficacy both in vitro and in vivo. These probiotics appear to be suitable for meeting the unmet need for new drugs for PKU. [ABSTRACT FROM AUTHOR]

This review discusses the epidemiology, pathophysiology, genetic etiology, and management of phenylketonuria (PKU). PKU, an autosomal recessive disease, is an inborn error of phenylalanine (Phe) metabolism caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene. The prevalence of PKU varies widely among ethnicities and geographic regions, affecting approximately 1 in 24,000 individuals worldwide. Deficiency in the PAH enzyme or, in rare cases, the cofactor tetrahydrobiopterin results in high blood Phe concentrations, causing brain dysfunction. Untreated PKU, also known as PAH deficiency, results in severe and irreversible intellectual disability, epilepsy, behavioral disorders, and clinical features such as acquired microcephaly, seizures, psychological signs, and generalized hypopigmentation of skin (including hair and eyes). Severe phenotypes are classic PKU, and less severe forms of PAH deficiency are moderate PKU, mild PKU, mild hyperphenylalaninaemia (HPA), or benign HPA. Early diagnosis and intervention must start shortly after birth to prevent major cognitive and neurological effects. Dietary treatment, including natural protein restriction and Phe-free supplements, must be used to maintain blood Phe concentrations of 120–360 μmol/L throughout the life span. Additional treatments include the casein glycomacropeptide (GMP), which contains very limited aromatic amino acids and may improve immunological function, and large neutral amino acid (LNAA) supplementation to prevent plasma Phe transport into the brain. The synthetic BH4 analog, sapropterin hydrochloride (i.e., Kuvan®, BioMarin), is another potential treatment that activates residual PAH, thus decreasing Phe concentrations in the blood of PKU patients. Moreover, daily subcutaneous injection of pegylated Phe ammonia-lyase (i.e., pegvaliase; PALYNZIQ®, BioMarin) has promised gene therapy in recent clinical trials, and mRNA approaches are also being studied. [ABSTRACT FROM AUTHOR]

Objective To explore the gene mutation frequency and characteristics of phenylalanine hydroxylase (PAH) in PAH deficiency children in some regions of Chongqing in order to provide scientific reference for the diagnosis and treatment of the disease. Methods A retrospective analysis was conducted on 45 children with PAH deficiency who were diagnosed in our hospital from January 1, 2014 to October 25, 2020. They was assigned into classic phenylketonuria (PKU), mild PKU and mild hyperphenylalaninemia (HPA). We analyzed the mutations of PAH gene by second-generation high-throughput sequencing and multiplex ligase probe dependent amplification (MLPA) technique, and the results were verified by the detection of corresponding mutation sites of their parents by Sanger sequencing. Results ① There were 2 mutation sites in 43 cases, including 40 cases of compound heterozygous mutation and 3 cases of homozygous mutation. All mutations were detected in the corresponding mutation sites of their parents. The left 2 cases had heterozygous mutations, and had only 1 mutation site. ② There were 34 types of mutations detected in 45 patients with PAH deficiency. Missense mutation was the main mutation type (52.9%). The mutation frequency of c.728G>A was the highest (15.9%, 14/88), followed by c.158G>A (11.4%, 10/ 88), c.1197A>T (9.1%, 8/88), and c.721C > T (9.1%, 8/88). The region of high frequency mutation was in exon 7, which contained 4 mutations and 26 mutations sites (29.5%). ③ There were 11 PAH gene mutations in 13 patients with classic PKU. The mutation frequency of c.728G> A (8/25, 32%) was the highest. There were 9 PAH gene mutations in 8 patients with mild PKU. The mutation frequency of c.728G>A (3/15, 20%) was the highest. There were 24 PAH gene mutations in 24 patients with mild HPA. The mutation frequency of c.158G>A (10/48, 20.8%). Conclusion The mutations in children with PAH deficiency in some regions of Chongqing are mainly compound heterozygosity. Missense mutation is the main type, with obvious hot spot mutations (c.728G>A, c.158G>A, c.721C > T and c.1197A>T).

Background: Metazoan guts are in permanent contact with microbial communities. However, the host mechanisms that have developed to manage the dynamic changes of these microorganisms and maintain homeostasis remain largely unknown. Results: Serotonin (5-hydroxytryptamine [5-HT]) was found to modulate gut microbiome homeostasis via regulation of a dual oxidase (Duox) gene expression in both Bactrocera dorsalis and Aedes aegypti. The knockdown of the peripheral 5-HT biosynthetic gene phenylalanine hydroxylase (TPH) increased the expression of Duox and the activity of reactive oxygen species, leading to a decrease in the gut microbiome load. Moreover, the TPH knockdown reduced the relative abundance of the bacterial genera Serratia and Providencia, including the opportunistic pathogens, S. marcescens and P. alcalifaciens in B. dorsalis. Treatment with 5-hydroxytryptophan, a precursor of 5-HT synthesis, fully rescued the TPH knockdown-induced phenotype. Conclusions: The findings reveal the important contribution of 5-HT in regulating gut homeostasis, providing new insights into gut–microbe interactions in metazoans. [ABSTRACT FROM AUTHOR]

Existing phenylalanine hydroxylase (PAH)-deficient mice strains are useful models of untreated or late-treated human phenylketonuria (PKU), as most contemporary therapies can only be initiated after weaning and the pups have already suffered irreversible consequences of chronic hyperphenylalaninemia (HPA) during early brain development. Therefore, we sought to evaluate whether enzyme substitution therapy with pegvaliase initiated near birth and administered repetitively to C57Bl/6- Pah enu2/enu2 mice would prevent HPA-related behavioral and cognitive deficits and form a model for early-treated PKU. The main results of three reported experiments are: 1) lifelong weekly pegvaliase treatment prevented the cognitive deficits associated with HPA in contrast to persisting deficits in mice treated with pegvaliase only as adults. 2) Cognitive deficits reappear in mice treated with weekly pegvaliase from birth but in which pegvaliase is discontinued at 3 months age. 3) Twice weekly pegvaliase injection also prevented cognitive deficits but again cognitive deficits emerged in early-treated animals following discontinuation of pegvaliase treatment during adulthood, particularly in females. In all studies, pegvaliase treatment was associated with complete correction of brain monoamine neurotransmitter content and with improved overall growth of the mice as measured by body weight. Mean total brain weight however remained low in all PAH deficient mice regardless of treatment. Application of enzyme substitution therapy with pegvaliase, initiated near birth and continued into adulthood, to PAH-deficient Pah enu2/enu2 mice models contemporary early-treated human PKU. This model will be useful for exploring the differential pathophysiologic effects of HPA at different developmental stages of the murine brain. [ABSTRACT FROM AUTHOR]

Phenylalanine hydroxylase (PAH), which belongs to the aromatic amino‐acid hydroxylase family, is involved in protein synthesis and pyomelanine production through the hydroxylation of phenylalanine to tyrosine. In this study, the crystal structure of PAH from Bacillus cereus ATCC 14579 (BcPAH) with an additional 280 amino acids in the C‐terminal region was determined. The structure of BcPAH consists of three distinct domains: a core domain with two additional inserted α‐helices and two novel auxiliary domains: BcPAH‐AD1 and BcPAH‐AD2. Structural homologues of BcPAH‐AD1 and BcPAH‐AD2 are known to be involved in mRNA regulation and protein–protein interactions, and thus it was speculated that BcPAH might utilize the auxiliary domains for interaction with its partner proteins. Furthermore, phylogenetic tree analysis revealed that the three‐domain PAHs, including BcPAH, are completely distinctive from both conventional prokaryotic PAHs and eukaryotic PAHs. Finally, biochemical studies of BcPAH showed that BcPAH‐AD1 might be important for the structural integrity of the enzyme and that BcPAH‐AD2 is related to enzyme stability and/or activity. Investigations into the intracellular functions of the two auxiliary domains and the relationship between these functions and the activity of PAH are required. [ABSTRACT FROM AUTHOR]

The aromatic amino acid hydroxylases (AAAHs) phenylalanine hydroxylase, tyrosine hydroxylase, and tryptophan hydroxylases 1 and 2 are structurally related enzymes that contain an active site iron atom and depend on tetrahydrobiopterin (BH 4 ) as cosubstrate. Due to their important roles in synthesis of serotonin, dopamine, noradrenaline, and adrenaline and their involvement in cardiovascular, neurological, and endocrine disorders, AAAHs have been targeted by substrate analogs, iron chelators, and allosteric ligands. Phenylalanine hydroxylase is also off-target of the histone deacetylase (HDAC) inhibitor panobinostat. To systematically explore the binding of HDAC inhibitors to AAAHs, we screened a library of 307 HDAC inhibitors and structural analogs against tryptophan hydroxylase 1 using a fluorescence-based thermal stability assay, followed by activity assays. Selected hits were enzymatically tested against all four purified human AAAHs. Cellular thermal shift assay was performed for phenylalanine hydroxylase. We show that panobinostat and structurally related compounds such as TB57, which similarly to panobinostat also contains a cinnamoyl hydroxamate, bind to human AAAHs and inhibit these enzymes with high selectivity within the class (panobinostat inhibition (IC 50 ): phenylalanine hydroxylase (18 nM) > tyrosine hydroxylase (450 nM) > tryptophan hydroxylase 1 (1960 nM). This study shows that panobinostat and related hydroxamic acid type HDAC inhibitors inhibit all AAAHs at therapeutically relevant concentrations. Our results warrant further investigations of the off-target relevance of HDAC inhibitors intended for clinical use and provide directions for new dual HDAC/AAAH and selective AAAH inhibitors. These findings may also provide a new mechanistic link between regulation of histone modification, AAAH function, and monoaminergic neurotransmission.

The metabolically promiscuous pentachlorophenol (PCP) hydroxylating Phe4MO (represented as CpsB) was detected, amplified (from the genome of Bacillus tropicus strain AOA-CPS1), cloned, overexpressed, purified and characterized here. The 1.755-kb gene cloned in the pET15b vector expressed a ≅ 64 kDa monomeric protein which was purified to homogeneity by single-step affinity chromatography, with a total yield of 82.1%. The optimum temperature and pH of the enzyme were found to be 30 °C and 7.0, respectively. CpsB showed functional stability between pH 6.0–7.5 and temperature 25–30 °C. The enzyme–substrate reaction kinetic studies showed the allosteric nature of the enzyme and followed pre-steady state using NADH as a co-substrate with apparent vmax, Km, kcat and kcat/Km values of 0.465 μM.s−1, 140 μM, 0.099 s−1 and 7.07 × 10−4 μM−1.s−1, respectively, for the substrate PCP. The in-gel trypsin digestion experiments and bioinformatic tools confirmed that the reported enzyme is a Phe4MO with multiple putative conserved domains and metal ion-binding site. Though Phe4MO has been reported to have a diverse catalytic function, here we report, for the first time, that it functions as a PCP dehalogenase or PCP-4-monooxygenase by hydroxylating PCP. Hence, the use of this enzyme may be further explored in the bioremediation of PCP and other related xenobiotics. [ABSTRACT FROM AUTHOR]

Phenylalanine hydroxylase (PAH) is involved in immune defence reactions by providing the starting material, tyrosine, to synthesise catecholamines and melanin. PAH is an important metabolic enzyme of aromatic amino acids and the rate-limiting enzyme in the hydroxylation of amino acid phenylalanine to tyrosine. In the present study, a PAH gene, LvPAH, was cloned and identified from Litopenaeus vannamei. The open reading frame (ORF) of LvPAH was 1383 bp, encoding a protein of 460 amino acids comprised of an ACT domain and a Biopterin_H domain. LvPAH was constitutively expressed in healthy L. vannamei , with the highest expression levels in the eyestalk and the lowest in the hepatopancreas. Both white spot syndrome virus (WSSV) and Vibrio parahaemolyticus infection upregulated LvPAH expression in hemocytes, hepatopancreas and gills of L. vannamei. Inhibition of LvPAH resulted in a significantly lower survival rate of L. vannamei after WSSV infection than the control group, consistent with the observation that WSSV viral load was significantly higher in LvPAH-silenced L. vannamei. After a V. parahaemolyticus challenge, there was no significant difference between the survival rate of LvPAH-silenced and the control L. vannamei. However, the load of V. parahaemolyticus in LvPAH-silenced L. vannamei was significantly higher than the control population for L. vannamei. The effect of LvPAH on L. vannamei from a neuroendocrinological perspective was assessed by measuring l -DOPA, dopamine (DA) and noradrenaline (NE) levels in the hemocytes after the knockdown of LvPAH. The results showed that phenoloxidase (PO), l -DOPA and DA levels in the hemolymph of LvPAH-silenced L. vannamei were significantly decreased starting from 24hpi. In contrast, the NE levels in the hemolymph of shrimp decreased significantly at first and then increased. The results suggest that LvPAH may play an important role in antiviral and bacterial immunity in L. vannamei. • PAH gene was cloned from Litopenaeus vannamei. • LvPAH expression could be induced by WSSV and Vibrio parahaemolyticus infection. • dsRNA-LvPAH injection significantly decreased the survival rates of L. vannamei after WSSV infection. • The loads of WSSV and V. parahaemolyticus in dsRNA-LvPAH injected L. vannamei were significant higher than the control. • The melanisation was regulated by LvPAH silence. [ABSTRACT FROM AUTHOR]

In the category of rare inherited genetic disorders, phenylketonuria is a prominent example. Here, the defective phenylalanine hydroxylase enzyme fails to catalyze conversion of phenylalanine to tyrosine. This leads to not only excess deposition of phenylalanine leading to phenylalanine toxicity but also precludes the production of important glutamatergic and cholinergic neurotransmitters, leading to epileptic disorders, microcephaly, low intelligence quotient etc. For long, specialized food products are considered as preferred solution to prevent disease outcome. Different medical diets are developed for managing phenylketonuria includes amino acid mixtures, protein hydrolysates, cofactor-based therapy, large neutral amino acids and glycomacropeptides. However, despite the advent of alternate forms of diet products, the central form of treatment has still been free amino acid mixture. The formulated diet is by and large expensive and in-depth evaluation of several factors which contribute to the expense of medicated diet is requisite to create effective yet affordable avenues for management of disease. For this, we have discussed the role of various factors involved in increasing price of medicated diet and presented possible solutions to it. We have also extensively reviewed prevalence of disease, commercial diet for PKU patients, and their associated limitations. Overall, this is the first attempt to present a holistic view of balance between the overall impact of diet associated therapy and weighing it against the associated finances incurred. [ABSTRACT FROM AUTHOR]

• The SNaPshot assay achieved the sensitivity and specificity of 91.6% and 100.0%, respectively. • The carrier rate was 1 in 58 (1.73%), and c.728G > A was the most common variant. • SNaPshot can accurately and rapidly detect PAH gene variants at a comparable performance and lower cost as compared with NGS. Hyperphenylalaninemia (HPA) is a common autosomal recessive disorder of phenylalanine metabolism, mainly caused by the deficiency of phenylalanine hydroxylase gene (PAH). A simple, fast, and accurate assay to achieve early diagnosis for children with HPA is required. In the present study, we established a SNaPshot-based assay that allows the simultaneous genotyping of 96 hotspot variants in the PAH gene. First, 18 Chinese HPA patients were analyzed by next generation sequencing (NGS) and SNaPshot in parallel. Then, the SNaPshot assay was performed to analyze the mutational spectrum of the PAH in 4,276 individuals in Eastern China. A total of 36 variants in the PAH gene were successfully identified by NGS, while the SNaPshot assay identified 34 PAH variants in these patients. Thus, the SNaPshot assay achieved the sensitivity and specificity of 91.6% and 100.0%, respectively. Furthermore, the carrier rate was approximately 1 in 58 (1.73%) in 4,276 individuals, and c.728G > A was the most common variant. In summary, SNaPshot can accurately and rapidly detect PAH gene variants at a comparable performance and lower cost as compared with NGS. Our results suggest that SNaPshot may serve as a promising approach for a routine genetic test in clinical practice. [ABSTRACT FROM AUTHOR]

Stroke is acute cerebrovascular injury, including ischemic and hemorrhagic strokes. It is an extremely debilitating and lethal disease that poses a significant threat to human health due to its high occurrence and poor prognosis. A variety of the biochemical factors may alter during or after the occurrence of a stroke, some of them may change before the incidence of stroke and may be considered as a major causes of it or they represent risk factors for stroke occurrence. Knowing of these changes represent a major goal for specialists in finding the appropriate therapies for treating strokes or to prevent it from occurring, or at least reduce the risk of stroke. Our study aimed to evaluate BH4, DHPR, PAH and MMP17 in hypertensive stroke patients in Basrah- Iraq, in order to know whether they represent biomarkers of ischemic stroke.The study included 50 patients with stroke (28 males and 22 females) aged between 44 to 67 years, which was admitted to Al-Sader Educational Hospital in Al-Basrah Government of Iraq, for the period extended between December 2019 to March 2020. A control group of 50 entirely healthy participants, with no chronic illnesses, no history of stroke, heart failure, or inflammation or infection in the previous two weeks and an age range of 46-65 years was chosen at random as 25 men and 25 women. The results of the study showed a significant increase in each of BH4 concentration and the activity of MMP17 in the stroke patients comparing to the control. From the results, we concluded that BH4 elevated significantly in patients with a moderate or severe ischemic stroke. This source of this elevation was not known. In the other hand MMP-17 showed a significant elevation in its activity only in the patients with a sever ischemic stroke. [ABSTRACT FROM AUTHOR]

Phenylketonuria (PKU) is the most frequent inborn disorder of amino acid metabolism caused by variants in human phenylalanine hydroxylase gene (PAH). In this study, a total of 109 PKU patients from Serbia were included, who were classified into three phenotypic categories in accordance with pre-treatment plasma phenylalanine level: classic PKU, mild PKU and mild hyperphenylalaninemia. For genetic analyses, we combined Sanger sequencing, MLPA and next generation sequencing to identify disease)causing variants in PAH gene, which were further classified using ACMG classification. Additionally, we used in silico and/or eukaryotic expression studies to assess the effect of novel genetic variants identified in our patients. Disease-causing variants were identified in 217 of 218 alleles, reaching detection rate of 99.5%. We detected a total of 32 different variants, of which 29 previously described and three novel ones: p.Gln226Lys, p.Pro244His and p.Pro416Leu. In silico and/or eukaryotic expression studies confirmed pathogenic effect of all novel genetic variants. The most frequent variant was p.Leu48Ser (31.2%), followed by p.Arg408Trp (13.8%), p.Ile306Val (9.2%). p.Glu390Gly (5%), p.Pro281Leu (4.6%), and p.Arg261Gln (3.2%). All detected disease-causing variants were classified as pathogenic using ACMG classification. Our study brings the updated spectrum of molecular genetic data, variant classification and detailed phenotypic characteristics for PKU patients from Serbia. Therefore, our study contributes to better understanding of molecular landscape of PKU in Europe and to general knowledge on genotype–phenotype correlation in PKU. [ABSTRACT FROM AUTHOR]

• In this review, we have discussed about an autosomal recessive metabolic disorder, Phenylketonuria (PKU), resulting from deficient phenylalanine hydroxylase (PAH) enzyme activity, leading to impaired phenylalanine (Phe) metabolism. • This review provides insights into pathophysiology, current treatment and diagnostic approaches. • We have further explored the wide array of sensors used till date for diagnosis of PKU. Phenylketonuria (PKU) is an autosomal recessive metabolic disorder resulting from deficient phenylalanine hydroxylase (PAH) enzyme activity, leading to impaired phenylalanine (Phe) metabolism. This condition can lead to intellectual disability, epilepsy, and behavioural issues. Treatment typically involves strict dietary restrictions on natural protein intake, supplemented with chemically manufactured protein substitutes containing amino acids other than Phe. Various approaches, including casein glycomacropeptide (GMP), tetrahydrobiopterin (BH 4), phenylalanine ammonia-lyase (PAL) therapy, large neutral amino acid (LNAA) supplementation, enzyme therapy, gene therapy, and medical therapies, aim to prevent Phe transport in the brain to potentially treat PKU. Although newborn screening programs and early dietary interventions have enhanced outcomes of the potential treatment strategies, limitations still persist in this direction. These involve potent accuracy concerns in diagnosis due to the existence of antibiotics in blood of PKU patients, affecting growth of the bacteria in the bacterial inhibition assay. Monitoring involves complex methods for instance, mass spectrometry and high-pressure liquid chromatography, which involve shortcomings such as lengthy protocols and the need for specialized equipment. To address these limitations, adaptable testing formats like bio/nano sensors are emerging with their cost-effectiveness, biodegradability, and rapid, accurate, and sensitive detection capabilities, offering promising alternatives for PKU diagnosis. This review provides insights into current treatment and diagnostic approaches, emphasizing on the potential applications of the diverse sensors intended for PKU diagnosis. [ABSTRACT FROM AUTHOR]

The functional role of long noncoding RNAs (lncRNAs) in inherited metabolic disorders, including phenylketonuria (PKU), is unknown. Here, we demonstrate that the mouse lncRNA Pair and human HULC associate with phenylalanine hydroxylase (PAH). Pair-knockout mice exhibited excessive blood phenylalanine (Phe), musty odor, hypopigmentation, growth retardation, and progressive neurological symptoms including seizures, which faithfully models human PKU. HULC depletion led to reduced PAH enzymatic activities in human induced pluripotent stem cellÐdifferentiated hepatocytes. Mechanistically, HULC modulated the enzymatic activities of PAH by facilitating PAH-substrate and PAH-cofactor interactions. To develop a therapeutic strategy for restoring liver lncRNAs, we designed GalNAc-tagged lncRNA mimics that exhibit liver enrichment. Treatment with GalNAc-HULC mimics reduced excessive Phe in Pair−/− and PahR408W/R408W mice and improved the Phe tolerance of these mice. [ABSTRACT FROM AUTHOR]

Inborn errors of metabolism are generally autosomal recessive inherited disorders. The incidence and genetic features of neonatal metabolic disorders vary significantly by regions and populations. In this study, we aimed to determine the amino acid metabolism disorders and evaluate the genetic test results of these patients retrospectively. The blood samples collected from heel blood and dried on filter cards in the neonatal screening program, were analyzed for amino acid metabolism disorders by (LC)-MS/MS method. Patients with suspected metabolic diseases were diagnosed with NGS method. Amino acid metabolism disorders were detected in 66 of 2,104 patients who were screened for suspected neonatal metabolic disorders. Sixty-two of 66 patients were diagnosed with phenylketonuria, the rest of them were diagnosed with tyrosinemia type I, arginosuccinate lyase deficiency, citrullinemia type 1 and Maple Tree syrup disease. The most common PAH gene mutations were c.1208C>T (A403V). Phenylketonuria was the most common disease among amino acid metabolism disorders in Şanlıurfa. There were different allele frequencies compared to the PAH mutations reported in previous studies. This may be due to the different characteristics of the populations and also the high rate of consanguineous marriage in our region. [ABSTRACT FROM AUTHOR]

Repetitive transcranial magnetic stimulation (rTMS) for treatment-resistant major depression offers an alternative therapy, since more than every third patient is not responding to adequate antidepressive treatment. In this interventional study safety, symptom development and changes of serum concentrations of neurotransmitter precursor amino acids, of immune activation and inflammation markers, of brain-derived neurotrophic factor (BDNF), nitrite as well as of salivary amylase were measured before and after a frontal polar cortex stimulation using rTMS as add-on treatment in 38 patients with treatment-resistant depression. Out of these, 17 patients received sham stimulation as a control. Treatment was well tolerated: with the exception of one patient of the verum group, who described discomfort during the second treatment, no serious adverse effects were observed. Improvement of depression with a significant decrease in the HAMD-7 scale (p = 0.001) was found in patients treated with rTMS, but not in sham-treated patients. Furthermore, serum phenylalanine and tyrosine dropped significantly (p = 0.03 and p = 0.027, respectively) in rTMS-treated patients. The kynurenine to tryptophan ratio (Kyn/Trp) tended to decrease under rTMS (p = 0.07). In addition, associations between concentrations of BDNF and neopterin as well as serum nitrite levels were found in patients after rTMS treatment, which indicates an influence of immune regulatory circuits on BDNF levels. In the sham-treated patients, no changes of biomarker concentrations were observed. Results show that rTMS is effective in the treatment of resistant depression. rTMS appears to influence the enzyme phenylalanine hydroxylase, which plays a central role in the biosynthesis of neurotransmitter precursors tyrosine and dihydroxyphenylalanine (DOPA). [ABSTRACT FROM AUTHOR]

In addition to tetrahydrobiopterin deficiencies and phenylalanine hydroxylase deficiency (phenylketonuria) due to PAH variants, the deficiency of the co-chaperone protein DNAJC12 was identified in 2017 as a novel cause of inherited hyperphenylalaninemia, revealing the genetic etiology in previously unresolved cases. In this study, we aimed to investigate DNAJC12 deficiency in non-tetrahydrobiopterin-deficient persistent hyperphenylalaninemia cases without biallelic PAH variants in a single pediatric metabolic center. It was determined retrospectively that 471 patients with non-tetrahydrobiopterin deficiency-hyperphenylalaninemia had undergone PAH gene sequencing and 451 patients had biallelic variants in PAH. DNAJC12 sequencing was performed in the remaining 20 patients, identifying a previously reported homozygous splice-site variant (c.158-2A > T) in one patient with axial hypotonia and developmental delay, and a novel, homozygous c.404del (p.Arg135Lysfs*21) frameshift variant in an asymptomatic patient. In segregation analysis, the asymptomatic patient's both parents were also found to be homozygous for this variant and hyperphenylalaninemic. The parents may have had academic difficulties but intellectual disability could not be confirmed due to lack of cooperation. The symptomatic patient significantly benefited from treatment with sapropterin dihydrochloride and neurotransmitter precursors. DNAJC12 deficiency might be responsible for approximately 10% or more of cases with unexplained hyperphenylalaninemia. The phenotypic spectrum is broad, ranging from early infantile hypotonia to incidental diagnosis in adulthood. Similar to tetrahydrobiopterin deficiencies, early diagnosis and treatment with sapropterin dihydrochloride and neurotransmitter precursors can be beneficial, supporting the analysis of DNACJ12 gene in patients with unexplained hyperphenylalaninemia. [ABSTRACT FROM AUTHOR]

Serotonin is an important signaling molecule in the periphery and in the brain. The hydroxylation of tryptophan is the first and rate-limiting step of its synthesis. In most vertebrates, two enzymes have been described to catalyze this step, tryptophan hydroxylase (TPH) 1 and 2, with expression localized to peripheral and neuronal cells, respectively. However, animals lacking both TPH isoforms still exhibit about 10% of normal serotonin levels in the blood demanding an additional source of the monoamine. In this study, we provide evidence by the gain and loss of function approaches in in vitro and in vivo systems, including stable-isotope tracing in mice, that phenylalanine hydroxylase (PAH) is a third TPH in mammals. PAH contributes to serotonin levels in the blood, and may be important as a local source of serotonin in organs in which no other TPHs are expressed, such as liver and kidney. [ABSTRACT FROM AUTHOR]

Background: Phenylketonuria (PKU) is one of the common Inborn Errors of Metabolism diseases, especially in a population with a high prevalence of consanguineous marriage that caused by a phenylalanine hydroxylase (PAH) deficiency or cofactor BH4. This systematic review and meta-analysis aimed to investigate the prevalence of PKU in Iran. Methods: The protocol of this systematic review was published in PROSPERO (CRD42024540811). The MOOSE protocol and the PRISMA guidelines were used. The Web of Sciences, PubMed/Medline, Sciences Direct, Google Scholar, Scopus, Civilica, IranDoc, and SID databases were searched 31/03/2024. The I2 index and Q test were used to check heterogeneity. Comprehensive meta-analysis software (CMA ver. 2) was used (P<0.05 is considered significant). Results: Finally, 20 studies with 1,992,090 Iranian neonates were included. The prevalence of non-severe PKU (Phe level: 2 or 4 until 20 mg/dl) was 75.6/100,000 (95% CI: 48.1-118.72). The prevalence of severe PKU (Phe level: =20 mg/dl) was 16.7/100,000 (95% CI: 13.6-20.5). The prevalence of PKU in girls and boys was 15.2/100,000 (95% CI: 5.2-44.2) and 9.8/100,000 (95% CI: 3.2-29.8), respectively. Subgroup analysis was performed based on region, province, and study quality. In addition, mixed effects meta-regression was used to find the relationship between continuous variables. Sensitivity analysis showed that the pooled estimate was robust. Conclusions: Iran has a high prevalence of PKU and consanguineous marriage, but it can be controlled by restricting diets and Phe-free formulas. Special attention needs to be paid to these patients, and their prevalence should be controlled. [ABSTRACT FROM AUTHOR]

Phenylalanine hydroxylase (PAH) is an allosteric enzyme that maintains phenylalanine (Phe) below neurotoxic levels; its failure results in phenylketonuria, an inborn error of amino acid metabolism. Wild type (WT) PAH equilibrates among resting-state (RS-PAH) and activated (A-PAH) conformations, whose equilibrium position depends upon allosteric Phe binding. The RS-PAH conformation of WT rat PAH (rPAH) contains a cation-π sandwich involving Phe80 that cannot exist in the A-PAH conformation. Phe80 variants F80A, F80D, F80L, and F80R were prepared and evaluated using native PAGE, size exclusion chromatography, ion exchange behavior, intrinsic protein fluorescence, enzyme kinetics, and limited proteolysis, each as a function of [Phe]. Like WT rPAH, F80A and F80D show allosteric activation by Phe while F80L and F80R are constitutively active. Maximal activity of all variants suggests relief of a rate-determining conformational change. Limited proteolysis of WT rPAH (minus Phe) reveals facile cleavage within a 4-helix bundle that is buried in the RS-PAH tetramer interface, reflecting dynamic dissociation of that tetramer. This cleavage is not seen for the Phe80 variants, which all show proteolytic hypersensitivity in a linker that repositions during the RS-PAH to A-PAH interchange. Hypersensitivity is corrected by addition of Phe such that all variants become like WT rPAH and achieve the A-PAH conformation. Thus, manipulation of Phe80 perturbs the conformational space sampled by PAH, increasing sampling of on-pathway intermediates in the RS-PAH and A-PAH interchange. The behavior of the Phe80 variants mimics that of disease-associated R68S and suggests a molecular basis for proteolytic susceptibility in PKU-associated human PAH variants. • Phenylalanine hydroxylase variants at Phe80 lack a stabilizing cation-π interaction. • A new and stable undocked phenylalanine hydroxylase conformation is revealed. • PKU-associated phenylalanine hydroxylase variants may favor this conformation. [ABSTRACT FROM AUTHOR]