Phenylketonuria: brain phenylalanine concentrations relate inversely to cerebral protein synthesis.

[phenylketonuria]

In phenylketonuria , elevated plasma phenylalanine concentrations may disturb blood -to -brain large neutral amino acid (LNAA ) transport and cerebral protein synthesis (CPS ). We investigated the associations between these processes , using data obtained by positron emission tomography with l-[1 -(11 )C ]-tyrosine ((11 )C-Tyr ) as a tracer . Blood -to -brain transport of non-Phe LNAAs was modeled by the rate constant for (11 )C-Tyr transport from arterial plasma to brain tissue (K 1 ), while CPS was modeled by the rate constant for (11 )C-Tyr incorporation into cerebral protein (k 3 ). Brain phenylalanine concentrations were measured by magnetic resonance spectroscopy in three volumes of interest (VOIs ): supraventricular brain tissue (VOI 1 ), ventricular brain tissue (VOI 2 ), and fluid-containing ventricular voxels (VOI 3 ). The associations between k 3 and each predictor variable were analyzed by multiple linear regression . The rate constant k 3 was inversely associated with brain phenylalanine concentrations in VOIs 2 and 3 (adjusted R (2 )=0 .826 , F =19 .936 , P =0 .021 ). Since brain phenylalanine concentrations in these VOIs highly correlated with each other , the specific associations of each predictor with k 3 could not be determined . The associations between k 3 and plasma phenylalanine concentration , K 1 , and brain phenylalanine concentrations in VOI 1 were nonsignificant . In conclusion , our study shows an inverse association between k 3 and increased brain phenylalanine concentrations .Journal of Cerebral Blood Flow & Metabolism advance online publication , 29 October 2014 ; doi :10 .1038 /jcbfm .2014 .183 .

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Diseases presenting "specific associations of each predictor" symptom

phenylketonuria

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