Efficacy of Phenylalanine- and Tyrosine-Restricted Diet in Alkaptonuria Patients on Nitisinone Treatment: Case Series and Review of Literature.
Annals of nutrition & metabolism, vol.78, no.1, pp.48-60, 2022 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 78 Issue: 1
- Publication Date: 2022
- Doi Number: 10.1159/000519813
- Journal Name: Annals of nutrition & metabolism
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Agricultural & Environmental Science Database, BIOSIS, CAB Abstracts, Chemical Abstracts Core, CINAHL, EMBASE, Food Science & Technology Abstracts, MEDLINE, Veterinary Science Database
- Page Numbers: pp.48-60
- Keywords: Alkaptonuria, Nitisinone, Tyrosine, phenylalanine-restricted diet, Amino acid supplementation
- Dokuz Eylül University Affiliated: Yes
Abstract
Introduction: Nitisinone used in alkaptonuria (AKU) can result in keratopathy due to strongly increased tyrosine levels. Methods: This study aimed to investigate nutritional status and changes in plasma tyrosine and phenylalanine and urinary homogentisic acid (u-HGA) levels in 8 adult AKU patients (mean age, 56.3 +/- 4.7 years) who were on tyrosine/phenylalanine-restricted diet together with 2 mg/day nitisinone. Results: The treatment period was 23.4 +/- 6.9 months. Daily dietary protein intake was restricted to 0.8-1.0 g/kg/day. Daily tyrosine intake was restricted to 260-450 mg/day for females and 330-550 mg/day for males. Tyrosine/phenylalanine-free amino acid supplements accounted for an average of 56.1% of daily protein intake. The following assessments were performed: anthropometric and plasma tyrosine level measurements every 2 months; ophthalmological examination every 6 months, and nutritional laboratory analyses and measurements of plasma amino acids and u-HGA once in a year. It was targeted to keep the plasma tyrosine level 700 mu mol/L was detected. The u-HGA level before and after the 1st year of treatment was 1,429.3 +/- 1,073.4 mmol/mol creatinine and 33.6 +/- 9.5 mmol/mol creatinine, respectively. None of the patients developed keratopathy or experienced weight loss and protein or micronutrient deficiency. Conclusion: AKU patients should receive tyrosine/phenylalanine-restricted diet for reducing plasma tyrosine level to the safe range. Tyrosine/phenylalanine-free amino acid supplements can be safely used to enhance dietary compliance. Keratopathy and nutrient deficiency should be frequently monitored.