Laurie Wideman, FACSM, Travis Anderson, Lenka Shriver, Cheryl Buehler, Esther Leerkes. UNC Greensboro, Greensboro, NC.

BACKGROUND: Previous data suggest that levels of certain metabolic and inflammatory biomarkers in cord blood impact obesity outcomes in childhood. But cord blood comingles biomarker concentrations from the mom and fetus, making it difficult to ascertain biomarker production in newborn infants or decipher the role of these biomarkers in later weight-related outcomes. PURPOSE: To measure changes in several urinary metabolic (i.e., insulin, leptin) and inflammatory (i.e., c-reactive protein (CRP), interleukin (IL)-6, tumor necrosis factor (TNF)-α) biomarkers across early infancy (age 2-24 months). METHODS: As part of a larger longitudinal study, mother-infant dyads (maternal age=28.3±4.5 years) were recruited for a study on prenatal and early life predictors of subsequent obesity. Pilot testing included 23 full-term infants (>38 weeks, 39% female, birth weight=3561±493 g), with urine samples at 2, 6, 12, and 24 months. Urine collection occurred at least 7 days after immunizations or illness. Following manufacturer guidelines, urinary biomarker analysis was completed with a multiplex assay that assessed all 5 biomarkers in a single run. Change across time was individually assessed for each biomarker via multilevel growth models. RESULTS: IL-6 and TNF-α levels were low (/ml) and remained stable across time. The number of samples with undetectable IL-6 levels was high at all time points (43-60%), while the undetectable levels for TNF-α were much lower (10-24%). CRP levels were detectable in all samples and were higher at 6 months (1004±3105 pg/ml), than at 2, 12 and 24 months (range: 135.1±309.0 to 245.1±749.0 pg/ml), but the difference was not significant. Leptin levels remained stable over the first 24 months (9-11 pg/ml), with undetectable levels in ~40% of samples at each time point. Insulin levels demonstrated a statistically significant increase in concentration from 2 (1.4±3.1 μIU) to 24 (4.2±4.8 μIU) months (p = 0.031), with undetectable levels dropping from 19% at 2 months to 0% at 24 months. CONCLUSIONS: Urinary metabolic and inflammatory biomarkers were detectable in most infant samples. As expected, given our collection criteria, urinary inflammatory biomarkers were low and relatively stable across the first 24 months of life. Insulin increased across infancy, with the largest change occurring from 6 to 12 months, likely reflecting changes in feeding (integration of solid foods into the diet).

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