Reemst, H. van (Hannah) (2018) The biochemical effects of phenylalanine supplementation on phenylalanine and tyrosine concentrations in blood in Hereditary Tyrosinemia type 1 patients :Should phenylalanine be regularly supplemented? thesis, Medicine.
Full text available on request.Abstract
Background: Hereditary Tyrosinemia type 1 (HT1) is a rare inborn error of amino acid tyrosine catabolism, caused by a fumarylacetoacetase deficiency. Treatment with the herbicide nitisone and a phenylalanine and tyrosine restricted diet has greatly improved the outcome. However, still clinical complications are found possibly related to low phenylalanine concentrations. Phenylalanine supplementation may be a possible treatment option to prevent these low phenylalanine concentration, but may also cause too high tyrosine concentrations. Therefore, this study investigated the biochemical effects of phenylalanine supplementation on phenylalanine and tyrosine concentrations and its variation, using different dosages of phenylalanine supplementation. By doing this, we tried to answer if phenylalanine supplementation could be advisable to administer regularly and the optimal dosage at which it should be given. Methods: The study lasted 24 days and was divided in three periods with different dosages of phenylalanine supplementation. Four patients took home blood spots three times daily for measuring phenylalanine and tyrosine concentrations. Statistical analyses were performed by using Friedman tests to study mean phenylalanine and tyrosine concentrations and variation. Correlation testing were done using Spearman and Pearson correlation tests. Patients have been individually described as well. Results: A positive correlation was found between phenylalanine supplementation and the phenylalanine concentrations in blood showing higher phenylalanine concentrations when receiving supplementation. Mean tyrosine concentrations greatly increased when receiving a dosage of 40 mg/kg/day. The Phe/Tyr ratio tended to be the most beneficial when 20 mg/kg/day of supplementation was given. Phenylalanine concentrations tended to show less variation when phenylalanine supplementation was given. Discussion: In conclusion, a dosage of 20 mg/kg/day of phenylalanine supplementation should be considered when patients frequently show low blood phenylalanine concentrations as this increases the phenylalanine concentrations, without causing too high tyrosine concentrations. Further studies are needed to investigate the influence of phenylalanine supplementation on the neurocognitive functions of HT1 patients.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Spronsen, Prof. Francjan vanM.D. P.h.D. and Ginkel, Wiggert van BSc and Beatrix Children’s Hospital and Department of Metabolic Diseases and University Medical Center of Groningen |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 11:03 |
| Last Modified: | 25 Jun 2020 11:03 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/2354 |
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