Circulating Cathelicidin Concentrations in a Cohort of Healthy Children: Influence of Age, Body Composition, Gender and Vitamin D Status

Abstract

Cathelicidin is an antimicrobial peptide whose circulating levels are related to vitamin D status in adults. This study sought to determine if circulating cathelicidin concentrations in healthy children are related to the age of the child, body composition and vitamin D status at birth and at the time of the study visit. Blood samples were obtained during yearly visits from 133 children, ages 2-7, whose mothers had participated in a pregnancy vitamin D supplementation RCT. Radioimmunoassay and ELISA were performed to analyze 25(OH)D and cathelicidin, respectively. Statistical analyses compared cathelicidin concentrations with concentrations of 25(OH)D at various time points (maternal levels throughout pregnancy, at birth, and child's current level); and with race/ethnicity, age, gender, BMI, percent fat, and frequency of infections using Student's t-test, χ2, Wilcoxon ranked-sum analysis, and multivariate regression. The cohort's median cathelicidin concentration was 28.1 ng/mL (range: 5.6-3368.6) and did not correlate with 25(OH)D, but was positively correlated with advancing age (ρ = 0.236 & p = 0.005, respectively). Forty patients evaluated at two visits showed an increase of 24.0 ng/mL in cathelicidin from the first visit to the next (p<0.0001). Increased age and male gender were correlated with increased cathelicidin when controlling for race/ethnicity, percent fat, and child's current 25(OH)D concentration (p = 0.028 & p = 0.047, respectively). This study demonstrated that as children age, the concentration of cathelicidin increases. Furthermore, male gender was significantly associated with increased cathelicidin concentrations. The lack of association between vitamin D status and cathelicidin in this study may be due to the narrow range in observed 25(OH)D values and warrants additional studies for further observation.

Fig 1. Cathelicidin Concentration by Age.

There was a significant positive correlation between age and cathelicidin concentration (ρ = 0.236, p = 0.005); ρ value represents Spearman correlation. The upper and lower edges of the box represent the 75^th percentile and the 25^th percentile of cathelicidin concentration, respectively, measured by ELISA and reported in ng/mL.

Fig 2. Change of Cathelicidin Concentration over Time.

In a subset of 40 children with two consecutive visits roughly twelve months apart, the median increase in cathelicidin concentration from the first visit to the second visit was 24.0 ng/mL (ranging from -1.9 ng/mL to +223.4ng/mL, p≤0.0001); ρ value represents Spearman correlation. The upper and lower edges of the box represent the 75^th percentile and the 25^th percentile of cathelicidin concentration, respectively, reported in ng/mL.