Impact Of A Phe-Restricted Diet On Gut Health In Children With PKU

Recruiting now

Conditions studied: Phenylketonuria

In brief

Phenylketonuria (PKU) is an inherited disorder of phenylalanine (Phe) metabolism. The mainstay of treatment is a Phe-restricted diet, which aims to maintain blood Phe concentrations within the recommended range and prevent neurological complications. Some individuals with PKU respond to pharmacological treatments, including sapropterin, a synthetic form of tetrahydrobiopterin (BH4), or sepiapterin. These treatments may increase Phe tolerance and allow a less restrictive diet. Diet is an important determinant of gut microbiota composition and function. However, the effects of the Phe-restricted diet and pharmacologically enabled dietary relaxation on the gut microbiota in PKU remain poorly understood. This observational study includes children and adolescents with PKU aged 3-17 years attending Birmingham Children's Hospital. Participants include those managed exclusively with a Phe-restricted diet, those receiving sapropterin, and those receiving sepiapterin. One healthy household control is recruited for each participant with PKU. Faecal samples are collected for shotgun metagenomic sequencing and metabolite profiling. Dietary intake, gastrointestinal symptoms, stool characteristics, clinical information, and PKU treatment are also assessed. The study investigates whether gut microbiota composition, microbial functional potential, and faecal metabolite profiles differ between participants managed with a Phe-restricted diet, those receiving pharmacological treatment, and healthy household controls. The findings may improve understanding of the relationships between PKU treatment, dietary restriction, gastrointestinal health, and the gut microbiome and may inform future nutritional strategies for individuals with PKU.

Key facts

Study ID

NCT07728032

Run by

Birmingham Women's and Children's NHS Foundation Trust

People needed

148

Starts

2025-10-01

Expected to finish

2026-12-01

Last updated by the study team

2026-07-27

Who can join

Age: 3 and older, up to 17. Sex: any. Healthy volunteers: accepted.

You may qualify if…

• Participants with PKU:
• Aged 3-17 years.
• Confirmed diagnosis of phenylketonuria following newborn screening.
• Receiving ongoing clinical management for PKU.
• For the diet-only cohort: managed with standard phenylalanine-restricted dietary treatment and not receiving sapropterin or sepiapterin.
• For the sapropterin cohort: receiving sapropterin for at least three consecutive months and having achieved at least a 100% increase in natural protein tolerance compared with the pre-treatment prescription.
• For the sepiapterin cohort: receiving sepiapterin for at least three consecutive months and having achieved at least a 100% increase in natural protein tolerance compared with the pre-treatment prescription.
• Healthy household controls:
• Aged 3 years or older.
• Living in the same household as a participating child or adolescent with PKU.
• No known diagnosis of PKU or another inherited metabolic disorder.

You may not qualify if…

• Congenital malformations.
• Chronic gastrointestinal disease.
• Endocrine, liver, or kidney disease.
• Other chronic medical conditions likely to affect gut microbiota composition.
• Following a therapeutic diet for a medical condition other than PKU within the six months before stool sample collection.

Where it is running

• Birmingham Children's Hospital — Birmingham, Birmingham, United Kingdom (enrolling)

Full record on ClinicalTrials.gov

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