FURKAN YOLCU, GÜLHAN SAMUR
Ankara Sağlık Bilimleri Dergisi - 2025;14(1):43-51
Leucine is a metabolic regulator with numerous important functions in the human body. Medical formulas used in patients with propionate metabolism disorders are devoid of propiogenic amino acids but contain disproportionately high amounts of leucine. Studies have indicated that the elevated leucine intake from these medical formulas may lead to unexpected adverse effects in patients with methylmalonic acidemia (MMA) and propionic acidemia (PA). In the dietary management of propionate metabolism disorders, restriction of natural protein intake and increased dependence on medical formulas often result in imbalanced leucine/valine and/or leucine/isoleucine ratios due to the excessive leucine content of these formulas. This imbalance can lead to decreased plasma levels of the essential amino acids valine and isoleucine. Additionally, elevated plasma leucine may reduce the transport of methionine across the blood–brain barrier, which is particularly concerning in cobalamin C (cblC) deficiency, where endogenous methionine synthesis is already impaired. The aim of this review is to draw attention to the potential nutritional implications of disease-specific medical formulas that are rich in leucine and free from propiogenic amino acids in the management of MMA, PA, and cblC deficiency, and to improve dietary recommendations. There is a clear need for further research to determine the optimal amino acid composition of medical formulas used in MMA and PA. Until such formulations are developed, the use of medical formulas should be approached with caution in the dietary management of MMA and PA, and disease-specific medical formulas should be avoided in patients with cobalamin C deficiency.
