Simplifying supplementation in MSUD: tolerance and acceptability of liquid valine and isoleucine supplements in maple syrup urine disease.

INTRODUCTION: Maple Syrup Urine Disease (MSUD) is a rare metabolic disorder requiring lifelong restriction of branched-chain amino acids (BCAAs), and targeted supplementation with valine and isoleucine to maintain metabolic stability. METHODS: A prospective, open-label, observational study was conducted over 56 days in 5 paediatric patients mean age 8.8 years (range 3–14) with classical MSUD. In Phase 1 (Days 0–28), participants received the ready to use (RTU) liquid valine formulation, while continuing their usual powdered isoleucine supplement. In Phase 2 (Days 29–56), participants returned to powdered valine and changed to the ready to use RTU liquid isoleucine supplement. Weekly plasma BCAAs were monitored. Acceptability, gastrointestinal tolerance, adherence, and dietary intake were assessed through questionnaires and food diaries. RESULTS: RTU liquid valine and isoleucine supplements were well tolerated and accepted by all participants. Plasma leucine decreased when taking both liquid valine (mean leucine 253 µmol/L) and isoleucine (mean leucine 219 µmol/L) compared to baseline (mean leucine 356 µmol/L). Required doses of valine and isoleucine decreased by 30% and 18%, respectively, suggesting improved adherence or enhanced efficacy. Palatability and ease of use were rated more favourably for the RTU products, with no adverse effects or adherence issues reported. Dietary intake remained stable throughout the study. DISCUSSION: These preliminary findings suggest that RTU valine and isoleucine formulations may offer potential advantages in MSUD management, simplifying administration, and enhancing user satisfaction. While limited by sample size and short-term evaluation, their practicality and patient-centered design warrant further investigation in larger, more diverse populations to establish long-term efficacy and broader applicability.