Dóra Becsei1, Ildikó Erni1, Erika Kiss1, Erika Simonová1, Ildikó Szatmári1, Attila Szabó1,2, János Bókay 1, Petra Zsidegh1,
1 1st Department of Pediatrics, Semmelweis University, Budapest, Hungary
2 MTA-SE Pediatric and Nephrology Research Group, Budapest, Hungary
Phenylketonuria (PKU) is an inherited metabolic disorder, caused by the deficiency of the phenylalanine hydroxylase enzyme. In poorly-treated cases, the patients have mental retardation. The background of cognitive impairment is not exactly clear. The one of the most important thesis based on facts that low tyrosine levels on the prefrontal cortex.
Our study is aimed to examine the correlations between cognitive functions and the serum phenylalanine, tyrosine and phenylalanine-to-tyrosine ratios. We studied the actual and lifelong-median metabolites.
The method of the cognitive examination was five tests from Cambridge Neuropsychological Test Automated Battery, called MOT, RTI, RVP, SOC and SWM. The tests can be used to study the reaction time, moving time, problem-solving skill, working memory and accuracy. The data were analysed with linear regressions using Microsoft Excel program and R statistical packages.
We collected 54 children with PKU, aged 4-18 years. The ratio of the boys is 50%.
None of the cognitive functions correlated with the serum tyrosine levels. SOC reaction time correlated with the actual Phe/Tyr ratio (intercept: 2119.48, factor 118.78, p: 0,03). SOC problem-solving skill is correlated with the actual Phe levels and with the median Phe/Tyr ratio. MOT reaction time, and MOT accuracy correlated with the lifelong-median Phe levels and Phe/Tyr ratio significantly.
PKU is an inherited metabolic disorder. Poorly-treated cases cause mental retardation. We examined cognitive functions of 54 children with PKU using 5 CANTAB tests. We examined the correlation between the cognitive functions and the actual and median phenylalanine tyrosine and phenylalanine-to-tyrosine ratio levels. 3 cognitive functions correlated with the median phenylalanine-to-tyrosine ratio. Our results may confirm the low tyrosine hypothesis in the prefrontal cortex, but more examinations are needed. In cognitive studies of children with PKU, is recommended to examine also the tyrosine and phenylalanine/tyrosine ratios.
Doctoral School: Clinical Medicine
Program: Prevention of chronic diseases in children
Supervisor: Petra Zsidegh