UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Aromatic amino acid requirements in human pregnancy and implications in maternal phenylketonuria management Ennis, Madeleine

Abstract

Background: During pregnancy there is an increased dietary requirement for most nutrients to allow for healthy growth and development of both the fetus and mother. Phenylalanine and tyrosine, two aromatic amino acids required for protein synthesis, are also key amino acids in the metabolic disorder phenylketonuria (PKU), which can be detrimental during pregnancy. The dietary requirements of phenylalanine and tyrosine for healthy human pregnancies have not been experimentally determined and publications about maternal PKU are limited. Objectives: (1) Determine the minimum dietary phenylalanine requirements during early and late gestation in healthy women, (2) determine the dietary requirements for phenylalanine and tyrosine (total aromatic amino acids, TAA) during early and late gestation in healthy women, and (3) describe current practices for managing maternal PKU and assess their efficacy. Methods: (1) Healthy pregnant women (n=23) were studied at a range of phenylalanine intakes (in the presence of excess tyrosine) in early and late pregnancy using stable isotope-based techniques (totaling 76 study days). (2) Healthy pregnant women (n=19) were studied at a range of phenylalanine intakes (in the absence of tyrosine) in early and late pregnancy using stable isotope-based techniques (totaling 51 study days). (3) A retrospective analysis of the dietitian’s records for 16 maternal PKU subjects was conducted at the Adult Metabolic Diseases Clinic at Vancouver General Hospital. Management practices, blood analyses, and dietary records were collected and analyzed. Results: (1) The minimum phenylalanine requirements were 15 and 21 mg·kg−¹·d−¹ during early and late pregnancy, respectively. (2) The TAA requirements were 44 and 50 mg·kg−¹·d−¹ in early and late pregnancy, respectively. (3) Current practices at the Adult Metabolic Diseases Clinic are working well to achieve metabolic control in individuals with maternal PKU. Conclusion: The results of the requirement studies will contribute to improved dietary recommendations for phenylalanine and tyrosine during pregnancy, as current recommendations are underestimated. The natural history provides reference values and management practices of maternal PKU patients, contributing to the limited data available and potentially improving clinical care and allow for future dietary requirement studies in this population. This dissertation adds novel data on phenylalanine and tyrosine metabolism and requirements during human pregnancies.

Item Citations and Data

License

Attribution-NonCommercial-NoDerivatives 4.0 International

Usage Statistics