Impact of brown adipose tissue vascular density on body adiposity in healthy Japanese infants and children

Background and Objective: The importance of brown adipose tissue (BAT) is well recognized in healthy infants and children. However, information regarding age-related changes in BAT vascular density (BAT-d) and the impact of BAT-d on body adiposity are lacking. This study aimed to evaluate the normal values of BAT-d, factors influencing BAT-d, and the impact of BAT-d on body adiposity in healthy infants and children. Methods: This study included 240 participants (127 girls and 113 boys) aged 1 month to 5 years. The tissue total hemoglobin concentration in the supraclavicular region adjusted according to the subcutaneous adipose tissue thickness (SAT) ([total-Hb-Adj](sup)) as BAT-d. SAT in the deltoid and interscapular regions (SAT(del+int)), the Kaup index (body weight [g]/height or length [cm]/height or length [cm] x 10) as body adiposity, and fertilization season were also measured. Results: The [total-Hb-Adj](sup) of boys was higher than that of girls (r = 0.277, p = 0.009). Younger children had a significantly higher Kaup index (r = 0.495, p < 0.001) and SAT(del+int) (r = 0.614, p < 0.001) than older children. Children who had higher [total-Hb-Adj](sup) had a significantly lower Kaup index (r = 0.495, p = 0.037) and SAT(del+int) (r = 0.614, p < 0.001). Conclusion: The [total-Hb-Adj](sup), as a parameter of BAT-d, is negatively correlated with body adiposity in children aged 1 month to 5 years, and BAT might affect human obesity to a much greater extent than expected. To prevent or treat obesity in early childhood, the level of BAT-d should be considered when using a dietary intervention.