Elevated Urine Creatinine in Relation to Protein Intake in Adolescent and Adult Females with Phenylketonuria (PKU) with Comparison to NHANES (P08-060-19)

Abstract

ObjectivesUrinary creatinine (UCr) excretion is a frequent protein metabolism marker, typically correlating directly to protein intake and muscle mass in healthy people. Because a standard PKU diet is low in intact protein (IP) with high intake of free amino acid medical food (MF), creatinine in PKU may differ from the general population. We compared UCr and Serum Cr (SCr) against NHANES values during five days of registered dietitian (RD) supervised diet management in a camp environment. MethodsAdolescent (11–17 yrs) and adult (18–53 yrs) females with PKU attending the 2018 Emory Department of Human Genetics Annual Metabolic Camp (Atlanta GA) consented to research. On days one and five, a random urine sample and fasting blood sample was collected for analysis of UCr and SCr (mg/dL), urine total protein (mg/L) (UTP), eGFR, BUN (mmol/L), and albumin (g/dL). Between days, campers adhered to MF and Phe intake as prescribed by their home RD. Three-day diet records were analyzed using Metabolic Pro. PKU cohort results for protein markers were compared to NHANES 2014 data for females of similar age. Data is reported as means (± SEM) (α = 0.05). ResultsFemales with PKU had UCr (Adol: 135 ± 22 [Day 1], 106 ± 20 [Day5], Adult: 127 ± 17 [Day1], 93.3 ± 13 [Day 5]) exceeding NHANES females (Mean: 76.9, CI: 72.4–81.6) at ≥65% on Day 1 and ≥ 21% on day 5. Adolescent SCr (Day1 & 5: 0.6 ± 0.02) specifically was less than NHANES (0.71 ± 0.01). eGFR was normal in all subjects indicating healthy kidney function. Mean TP intake (Days 1&5: 55–60 g/day by age) measured less than NHANES (Means: 59–73 g/day by age), as did kcal reported, with minimal change by day 5. Adolescent MF protein (MFP) intake increased (MFP: IP ratio: 4.3 vs 6.0, P = 0.026) (Adults: ns), albeit without correlation to UCr or SCr. ConclusionsCr excretion in females with PKU was higher than NHANES; SCr comparably lower in adolescents with PKU; TP and kcal intake was below NHANES. Although MFP: IP ratio improved in tandem with lowered UCr after five days, lack of significant correlation implicates other factors in Cr differences among this PKU cohort. Further study is required to determine crucial mechanisms inovoved and clinical relevance. Funding SourcesSupported in part by the National Center for Advancing Translational Sciences of the NIH under Award number ULITR002378.