Does protein intake correlate with tubular function in very preterm neonates?

Background High protein intake in very preterm neonates (VPN) is important for growth. However, preterm kidneys have fewer functional nephrons and many of the ones present may be immature. Studies have shown that high protein intake induces nephron hypertrophy, proteinuria, and glomerular sclerosis, which lead to tubular injury. Urinary neutrophil gelatinase-associated lipocalin (uNGAL) is a biomarker that is released during proximal tubular cell injury. The uNGAL to creatinine (uNGAL/Cr) ratio is commonly performed for normalization. Objective To assess for a possible association between protein intake and uNGAL/Cr ratio in VPN. Methods A prospective cohort study was conducted in two NICUs in Jakarta. Subjects’ urine specimens were collected at 0-48 hours, 72 hours, and 21 days after birth to determine uNGAL/Cr ratio as a biomarker of tubular injury. Protein was administered according to study sites NICU guidelines. Protein intake was recorded daily from 14-21 days of age for formula and measured twice with a human milk analyzer for breast milk. ELISA was used to measure uNGAL concentration. Low protein intake was defined as