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- Title
Tyrosine metabolism in health and disease: slow-release amino acids therapy improves tyrosine homeostasis in phenylketonuria.
- Authors
Porta, Francesco; Giorda, Sara; Ponzone, Alberto; Spada, Marco
- Abstract
Objectives: Phenylalanine (Phe) hydroxylase (PAH) deficiency leads to hyperphenylalaninemia (HPA) and tyrosine (Tyr) depletion. We investigated Tyr homeostasis in patients with PAH deficiency and the effect of a slow-release amino acids therapy in phenylketonuria (PKU). Methods: We performed four complementary investigations: (1) Tyr concentrations were monitored in 114 patients (10.6 ± 11.9 years) with PKU on dietary treatment supplemented with traditional amino acid formulations (n=52, 1175 samples) or non-PKU HPA on a free diet (n=62, 430 samples); (2) Tyr metabolism in PKU was quantitatively evaluated in three patients by a simple Tyr oral loading test (100 mg/kg); (3) diurnal and (4) long-term Tyr concentrations were evaluated in 5 and 13 patients with PKU, respectively, who switched from traditional to slow-release amino acids therapy. Results: 1) Tyr concentrations in the PKU population were subnormal and significantly lower than in non-PKU HPA (p<0.01); (2) the response to a Tyr loading test in PKU was normal, with basal Tyr concentrations reached within 12 h; (3) the diurnal metabolic profile in patients on slow-release amino acids therapy revealed higher morning fasting and nocturnal Tyr concentrations with respect to traditional therapy (p<0.01); (4) this picture was confirmed at follow-up, with normalization of morning fasting Tyr concentrations in patients on slow-release amino acids therapy (p<0.01) and unchanged Phe control (p=0.19). Conclusions: Slow-release amino acids therapy can improve Tyr homeostasis in PKU. If associated to optimized Phe control, such a metabolic goal may allow long-term clinical benefits in patients with PKU.
- Publication
Journal of Pediatric Endocrinology & Metabolism, 2020, Vol 33, Issue 12, p1519
- ISSN
0334-018X
- Publication type
Article
- DOI
10.1515/jpem-2020-0319