NCT07220265

Impact of Phenylalanine Elevations on Brain and Cognition in Adult PKU Carriers

The Impact of Phenylalanine Elevations on Metabolic, Cognitive, and Neural Functioning in Adults Heterozygous for Phenylketonuria (PKU)

• Status: Recruiting
• Phase: N/A
• Study type: Interventional
• Enrollment: 36 (estimated)
• Sponsor: University of Missouri-Columbia · Academic / Other
• Sex: All
• Age: 18 Years – 60 Years
• Healthy volunteers: Accepted

Summary

The goal of this clinical trial is to advance our understanding of the cognitive and neurophysiologic sequelae associated with suboptimal phenylalanine (Phe) metabolism in heterozygous carriers of phenylketonuria (PKU). The main questions it aims to answer are: * Do PKU carriers experience prolonged elevations in brain Phe levels following oral ingestion of dietary Phe? * Do PKU carriers experience disruptions in cognitive functioning following oral ingestion of dietary Phe? * Do PKU carriers experience atypical brain activity following oral ingestion of dietary Phe? Researchers will compare PKU carriers and non-carriers following oral ingestion of dietary Phe and a placebo. Participants will: * Consume Phe or a placebo at two separate visits to our facility * At each visit, they will complete a series of MRIs and cognitive tests throughout the day

Detailed description

Limitations inherent in past studies of phenylketonuria (PKU) carriers (e.g., poor genetic characterization of sample resulting in inclusion of homozygous non-PKU relatives, reliance on rudimentary or overly broad behavioral assessment tools) make it difficult to conclude the extent to which neurophysiologic and cognitive processes are affected in these individuals. To address this gap in the literature, we propose to conduct a double-blind crossover study in a sample of genetically-confirmed sample of 18 heterozygous PKU carriers and 18 non-carriers. A principled investigation of the effects of elevated phenylalanine (Phe) on neurocognition will involve participants performing an fMRI n-back WM task, resting state scan, and a battery of select cognitive tests at 3 timepoints: baseline (pre-load), 2 hours and 4 hours after starting oral administration of Phe or placebo. Blood and brain levels of Phe and Tyr will also be assessed at each timepoint.

Conditions

• Carrier of Phenylketonuria
• Healthy

Interventions

Type	Name	Description
DIETARY_SUPPLEMENT	Phenylalanine (Phe)	Oral ingestion of phenylalanine (Phe)
DIETARY_SUPPLEMENT	Placebo	Oral ingestion of Placebo (Vitamin C)

Timeline

• Start date: 2025-12-19
• Primary completion: 2026-12-31
• Completion: 2026-12-31
• First posted: 2025-10-23
• Last updated: 2026-03-11

Locations

1 site across 1 country: United States