A comparative study of the amino acid profile of urine during the development of undifferentiated connective tissue dysplasia (UCTD) in primary school-aged and adolescent children

The relationship between urinary amino acids and the pathophysiological mechanisms of undifferentiated connective  tissue  dysplasia  (UCTD)  development  in  children  of  different  ages  remains  relevant  for  early diagnosis. The aim of the study was to identify the stages of development of undifferentiated CTD in early schoolage children (7–10 years) and adolescents (11–15 years) by determining the amino acid composition of urine. A comparative study of the urine amino acid profile was conducted in children with undifferentiated connective tissue dysplasia (UCTD) of primary school age (7–10 years) and adolescents (11–16 years) living in the Sakha Republic (Yakutia). In primary school-aged children, as connective tissue (CT) disorders worsened (from grade 1 to grades 2-3 uCTD), elevated levels of not only CT disorder biomarkers such as 5-hydroxyproline and hydroxyproline were detected, but also amino acids such as glycine, proline, as well as serine and threonine, which participate in hydroxylation reactions and the synthesis of extracellular matrix proteins. This may indicate an early disturbance of amino acid metabolism underlying connective tissue disorders. The following groups of amino acids were identified that underwent the greatest changes in children of different ages with uCTD: amino acids associated with collagen metabolism (glycine, proline, hydroxyproline, and 5-hydroxyproline), branched-chain amino acids (valine, leucine, isoleucine), acidic amino acids (aspartate, glutamate), and aromatic amino acids (phenylalanine, tyrosine). The results of the study make a definite contribution to the development of modern ideas about the peculiarities of the formation of adaptive reactions of an organism living in extreme environmental conditions.

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