Brown adipose tissue in prepubertal children: associations with sex, birthweight, and metabolic profile.

Abstract

Individuals born small-for-gestational age (SGA), especially those who experience postnatal catch-up growth, are at increased risk for developing endocrine-metabolic abnormalities before puberty. In adults, brown adipose tissue (BAT) has been associated with protection against metabolic disorders, such as obesity, type 2 diabetes, and dyslipidaemia. Here, we assessed for the first time whether BAT activation differs between prepubertal children born SGA or appropriate-for-gestational age (AGA). The study population consisted of 86 prepubertal children [41 AGA and 45 SGA; age (mean ± SEM), 8.5 ± 0.1 years], recruited into two prospective longitudinal studies assessing endocrine-metabolic status and body composition in infancy and childhood. The temperature at the supraclavicular region (SCR) before and after a cold stimulus was measured by infrared thermal imaging, and the area of thermally active SCR (increase after cold challenge, ΔAreaSCR) was calculated as a surrogate index of BAT activation. The results were correlated with clinical, endocrine-metabolic, and inflammation variables, and with visceral and hepatic adiposity (assessed by Magnetic Resonance Imaging). No differences in BAT activation index, as judged by ΔAreaSCR, were found between AGA and SGA children. However, girls showed higher baseline and post-cold induction AreaSCR than boys (both p ≤ 0.01). An interaction between gender and birth weight subgroup was observed for BAT activation; AGA girls increased significantly the ΔAreaSCR as compared to AGA boys; this increase did not occur in SGA girls vs SGA boys. Cold-induced ΔAreaSCR negatively correlated with HOMA-IR, us-CRP, liver volume, and liver fat. Prepubertal AGA girls had significantly greater BAT activation index as compared to AGA boys; this difference was not observed in SGA subjects. Higher BAT activation associated with a lower amount of visceral fat and with a favorable metabolic profile. Long-term follow-up is needed to determine whether those differences relate to pubertal timing, and to the development of obesity and metabolic disorders.