Data on phenylalanine-to-tyrosine ratios in assessment of tetrahydrobiopterin (BH4)-responsiveness in patients with hyperphenylalaninemia

Barbka Repic Lampret; Mojca Zerjav Tansek; Blaz Groselj; Jaka Sikonja; Tadej Battelino; Urh Groselj

doi:10.1016/j.dib.2022.107926

Data on phenylalanine-to-tyrosine ratios in assessment of tetrahydrobiopterin (BH₄)-responsiveness in patients with hyperphenylalaninemia

Data Brief. 2022 Feb 4:41:107926. doi: 10.1016/j.dib.2022.107926. eCollection 2022 Apr.

Authors

Barbka Repic Lampret¹, Mojca Zerjav Tansek^{2

3}, Blaz Groselj^{3

4}, Jaka Sikonja³, Tadej Battelino^{2

3}, Urh Groselj^{2

3}

Affiliations

¹ Clinical Institute for Special Laboratory Diagnostics, University Children's Hospital, UMC Ljubljana, Ljubljana 1000, Slovenia.
² Department of Pediatric Endocrinology, Diabetes and Metabolic Diseases, University Children's Hospital, UMC Ljubljana, Ljubljana 1000, Slovenia.
³ Faculty of Medicine, University of Ljubljana, Ljubljana 1000, Slovenia.
⁴ Institute of Oncology Ljubljana, Ljubljana 1000, Slovenia.

Abstract

Blood phenylalanine-to-tyrosine (Phe/Tyr) ratio is an important indicator of metabolic control in phenylketonuria patients. We present the data that highlights the role of Phe/Tyr-ratio in the evaluation of tetrahydrobiopterin (BH₄)-responsiveness in patients with hyperphenylalaninemia. Our data complements the results from the original research article by Tansek et al., 2012 [1]. We performed a BH₄-loading test in 32 patients after four days of increased protein intake (2000 mg/kg body weight). Blood sampling was performed 96, 72, 48, 24, 16 h, and moments before oral administration of BH₄ in a dose of 20 mg/kg body weight. Additional blood samples were collected 8 and 24 h after its administration. Phenylalanine (Phe) and Tyrosine (Tyr) levels were determined from dried blood spots by tandem mass spectrometry. Phe/Tyr-ratio reached a plateau after three days of increased dietary protein intake. Fifteen patients (47%) responded to BH₄, defined as a decrease of Phe-of at least 30% after 24 h of BH₄ administration. Phe/Tyr-ratios were significantly higher in non-responders compared to responders. In the responder group, Phe/Tyr-ratios decreased in average of 67% (p = 0.001) and 45% (p = 0.001) after 8 and 24 h of BH₄ administration, respectively. Phe/Tyr-ratio decreased after 8 h of drug administration also in the non-responder group, but not 24 h after administration.

Keywords: BH4, tetrahydrobiopterin; BH4-responsiveness; F, female; Hyperphenylalaninemia; M, male; MHP, mild hyperphenylalaninemia; NI, not included; NR, non-responder; Phe, phenylalanine; Phe/Tyr-ratio, phenylalanine-to-tyrosine ratio; Phenylalanine-to-tyrosine ratio; Phenylketonuria; R, responder; Tandem mass spectrometry; Tetrahydrobiopterin; Tyr, tyrosine; cPKU, classic phenylketonuria; mPKU, mild phenylketonuria.