2026-07-12 | Nutritional and Metabolic Management of Phenylketonuria: Integrating Dietary Strategies, Medical Nutrition Therapy, and Emerging Treatments.

Phenylketonuria (PKU) is an inherited metabolic disorder characterized by impaired phenylalanine metabolism, leading to neurotoxicity if untreated. Lifelong dietary restriction remains the cornerstone of management; however, adherence challenges and evolving therapeutic options necessitate an integrated approach to treatment. A comprehensive literature review was conducted using PubMed, Scopus, and Web of Science databases, including clinical studies, systematic reviews, and preclinical investigations published between 2007 and 2025. Current dietary strategies, medical nutrition therapies, and emerging pharmacological and gene-based treatments were evaluated. Nutritional management, particularly phenylalanine-restricted diets supported by medical foods such as amino acid mixtures and glycomacropeptide, remains essential for metabolic control. Adjunctive strategies, including large neutral amino acid supplementation and tetrahydrobiopterin therapy, may enhance dietary flexibility in selected patients. Enzyme substitution therapy with pegvaliase provides substantial reductions in blood phenylalanine levels and improves dietary liberalization. Emerging gene-editing approaches, including CRISPR-based technologies, offer potential long-term therapeutic benefits, although they remain in early developmental stages. Effective management of PKU requires a multidisciplinary and personalized approach integrating nutritional, pharmacological, and emerging molecular therapies. While dietary management continues to be fundamental, novel therapeutic strategies may significantly improve long-term outcomes and quality of life in individuals with PKU.

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2026-07-10 | Phenylketonuria in Saudi Arabia: An Overview of Diagnosis, Genetics, and Therapeutic Strategies

Phenylketonuria (PKU) is an autosomal recessive inborn error of phenylalanine (Phe) metabolism caused by pathogenic variants in the phenylalanine hydroxylase (PAH) gene, resulting in toxic phenylalanine accumulation that, if untreated, causes profound intellectual disability and neurodevelopmental impairment. PKU is especially significant in the Kingdom of Saudi Arabia (KSA), where high consanguinity rates substantially elevate disease prevalence relative to Western populations, and the country’s expanding newborn screening programs have highlighted PKU as a persistent public health concern. This review provides a translational synthesis of the Saudi PKU literature, covering epidemiology, molecular pathophysiology, genetics, clinical presentation, diagnosis, treatment, prognosis, and future directions. We summarize global and regional incidence data and show that Saudi Arabia, driven by consanguinity, is among the countries with the highest reported PKU burden worldwide. We review the metabolic basis of phenylalanine neurotoxicity and the allelic heterogeneity of the PAH gene, with attention to variants enriched in Saudi and Arab cohorts, including the founder allele p.R252W. Diagnostic pathways anchored in newborn screening and tandem mass spectrometry are discussed alongside neurodevelopmental outcomes and gaps in Saudi PKU surveillance. We outline established and emerging therapies, including dietary management, sapropterin (BH4), pegvaliase, large neutral amino acids, and investigational gene and mRNA therapies. Throughout, we identify where genuine Saudi-specific evidence exists and where general PKU knowledge is extrapolated to the Saudi context because of limited local data, most notably the absence of a national PKU registry. This review is intended to serve as a translational reference for clinicians, metabolic dietitians, geneticists, and policymakers engaged in PKU care in Saudi Arabia and the wider Arab region.

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2026-07-09 | Phenylalanine Transport through LAT1: Insights from Molecular Dynamics, Steered Molecular Dynamics, and Targeted Molecular Dynamics.

L-type amino acid transporter 1 (LAT1) is a heterodimeric membrane protein that primarily facilitates the transport of phenylalanine, along with other amino acids such as valine, leucine, isoleucine, tryptophan, and tyrosine across the cell membrane. It is predominantly expressed at the blood-brain barrier. While LAT1 has been extensively studied in the context of drug delivery, its specific transport pathway for phenylalanine and the related conformational dynamics remains largely unexplored. Investigation of the transport pathway of phenylalanine via LAT1 is also very important, as excessive amounts of phenylalanine can cause phenylketonuria (PKU). Inhibiting LAT1's transport could reduce phenylalanine's entry into the brain, aiding in the management of its levels and alleviating the adverse effects of PKU. To investigate the phenylalanine transport mechanism and the conformational dynamics of LAT1, microsecond-long molecular dynamics (MD) as well as steered molecular dynamics (SMD) and targeted molecular dynamics (TMD) simulations were performed. The results of this study identify essential structural motifs that enable the isomerization of LAT1 among outward-facing, inward-facing, and occluded states. A significant conclusion drawn from this research is the identification of seven critical transmembrane helices that play central roles along the transport pathway, namely, TM1, TM4, TM6, TM7, TM8, TM9, and TM12. Root-mean-square deviation (RMSD) analyses across the structural models further indicate that TM1 and TM6 are consistently engaged during both extracellular and intracellular phenylalanine transitions, whereas TM9 and TM12 contribute more specifically to the outward and inward opening events, respectively. The observed conformational changes offer fresh insights into the alternating-access mechanism of LAT1 during phenylalanine transport, contrasting with conclusions from structural models based on other substrates transport through LAT1. By elucidating this transport mechanism, the study will contribute to developing LAT1 inhibitors that can selectively regulate brain phenylalanine levels without disrupting the transport of other essential amino acids.

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