ESPE Abstracts

Background: Growth in infancy is considered primarily to be regulated by nutrition and insulin, whereas less is known about the influence of IGF-I, reproductive hormones and other factors of importance. Recently, paternally inherited genetic defects of DLK1 (Delta-like 1 homolog) were found in girls with central precocious puberty (CPP) with a metabolic phenotype. In addition, low maternal serum DLK1 concentrations were significantly lower in pregnant women who delivered an SGA newborn compared to controls. Knowledge about circulating DLK1 during minipuberty and the association to changes in linear growth and body composition needs further clarification.

Objective: To evaluate longitudinal changes in serum DLK1 concentrations during female minipuberty compared to changes in linear growth body mass index (BMI) and fat mass.

Method: In a prospective, longitudinal study (The COPENHAGEN Minipuberty Study, ClinicalTrials.gov ID: NCT02784184) between 2016 to 2018, we examined 233 healthy term children born AGA (114 females), at birth and up to six times within the first year of life. Length was measured in supine position to the nearest 0.5 cm with a baby length measuring mat (ADE Germany GmbH & Co, Hamburg, Germany). Weight was measured on an electronical calibrated scale (Babyscale, Solotop Oy, Finland) to the nearest 0.005 kg. Body fat percentage was calculated by Slaughter’s equation using triceps and subscapular skinfolds. At each visit a blood sample (n=206) were attempted in all female infants and then analysed for DLK1, growth factors and reproductive hormone. Serum DLK1 was assessed by an immunoassay (ELISA) (Immuno-Biological Laboratories, Inc (IBL-America), Minneapolis, USA) with a detection limit of 336 pg/ml.

Results: Serum DLK1 in girls was detectable in all longitudinal samples (100% > LOD) with an overall mean (SD) concentration of 17.4 ng/ml (3.5) (n=43) within the first month of life, followed by a log-linear decline through the first year of life. At 12 months of age, the mean (SD) DLK1 concentration was 9.5 ng/ml (2.4) (n=26). We did not find a correlation between mean DLK1 level (SDS) for each individual and the mean BMI SDS (Pearson Correlation coefficient -0.01, P=0.9).

Conclusion: Serum DLK1 declined significantly during the first year of life in healthy infant girls born AGA. In our initial analyses, we did not find any significant correlation between DLK1 and BMI in infant girls.