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

Background/Objectives 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). Subjects/methods 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, ΔArea SCR ) 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). Results No differences in BAT activation index, as judged by ΔArea SCR , were found between AGA and SGA children. However, girls showed higher baseline and post-cold induction Area SCR than boys (both p ≤ 0.01). An interaction between gender and birth weight subgroup was observed for BAT activation; AGA girls increased significantly the ΔArea SCR as compared to AGA boys; this increase did not occur in SGA girls vs SGA boys. Cold-induced ΔArea SCR negatively correlated with HOMA-IR, us-CRP, liver volume, and liver fat. Conclusions 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.