Assessment of catabolic state in infants with the use of urinary titin N-fragment

Abstract

Background: Urinary titin N-fragment levels have been used to assess the catabolic state, and we used this biomarker to evaluate the catabolic state of infants.

Methods: We retrospectively measured urinary titin N-fragment levels of urinary samples. The primary outcome was its changes according to postmenstrual age. The secondary outcomes included differences between gestational age, longitudinal change after birth, influence on growth, and relationship with blood tests.

Results: This study included 219 patients with 414 measurements. Urinary titin N-fragment exponentially declined with postmenstrual age. These values were 12.5 (7.1-19.6), 8.1 (5.1-13.0), 12.8 (6.0-21.3), 26.4 (16.4-52.0), and 81.9 (63.3-106.4) pmol/mg creatinine in full, late, moderate, very, and extremely preterm infants, respectively (p < 0.01). After birth, urinary levels of titin N-fragment exponentially declined, and the maximum level within a week was associated with the time to return to birth weight in preterm infants (ρ = 0.39, p < 0.01). This was correlated with creatine kinase in full-term infants (ρ = 0.58, p < 0.01) and with blood urea nitrogen in preterm infants (ρ = 0.50, p < 0.01).

Conclusions: The catabolic state was increased during the early course of the postmenstrual age and early preterm infants.

Impact: Catabolic state in infants, especially in preterm infants, was expected to be increased, but no study has clearly verified this. In this retrospective study of 219 patients with 414 urinary titin measurements, the catabolic state was exponentially elevated during the early postmenstrual age. The use of the urinary titin N-fragment clarified catabolic state was prominently increased in very and extremely preterm infants.