Brown Adipose Tissue, Adiposity, and Metabolic Profile in Preschool Children

Abstract

Context: An inverse relationship between brown adipose tissue (BAT) and obesity has previously been reported in older children and adults but is unknown in young children.

Objective: We investigated the influence of BAT in thermoneutral condition on adiposity and metabolic profile in Asian preschool children.

Design, setting, and participants: A total of 198 children aged 4.5 years from a prospective birth cohort study, Growing Up in Singapore Towards Healthy Outcomes (GUSTO) were successfully studied with water-fat magnetic resonance imaging of the supraclavicular and axillary fat depot (FDSA). Regions within FDSA with fat-signal-fraction between 20% and 80% were considered BAT, and percentage BAT (%BAT; 100*BAT volume/ FDSA volume) was calculated.

Main outcome measures: Abdominal adipose tissue compartment volumes, ectopic fat in the soleus muscle and liver, fatty liver index, metabolic syndrome scores, and markers of insulin sensitivity.

Results: A 1% unit increase in %BAT was associated with lower body mass index, difference (95% CI), -0.08 (-0.10, -0.06) kg/m2 and smaller abdominal adipose tissue compartment volumes. Ethnicity and sex modified these associations. In addition, each unit increase in %BAT was associated with lower ectopic fat at 4.5 years in the liver, -0.008% (-0.013%, -0.003%); soleus muscle, -0.003% (-0.006%, -0.001%) of water content and lower fatty liver index at 6 years.

Conclusions: Higher %BAT is associated with a more favorable metabolic profile. BAT may thus play a role in the pathophysiology of obesity and related metabolic disorders. The observed ethnic and sex differences imply that the protective effect of BAT may vary among different groups.

Keywords: adiposity; brown fat; metabolic profile; preschool children.

Figure 1.

Study flow chart showing children participating in MRI at 4.5 years.

Figure 2.

Color map of supraclavicular and axillary fat depots from water-fat MRI images in preschool children. Segmented supraclavicular and axillary fat depots (FD_SA) were indicated by white boundaries. Color map of fat-signal-fractions is illustrated on 0% (blue) to 100% (red) scale. Supraclavicular-axillary fat depots (outlined white) exhibit lower fat fractions in a child with BMI 13.5 kg/m² (A) vs a child with BMI 25.0 kg/m² (B).

Figure 3.

Scatter plots of child’s body mass index and brown and white adipose tissue within supraclavicular and axillary fat depot at 4.5 years. Scatter plots of child’s BMI and brown and white adipose tissue within supra-clavicular fat depot at 4.5 years. (A) The association between BMI and volume of brown adipose tissue; (B) the association between BMI and percentage of brown adipose tissue; (C) the association between BMI and volume of white adipose tissue; and (D) the association between BMI and percentage of white adipose tissue within supraclavicular and axillary fat depot.

Figure 4.

Histogram of fat-signal-fraction of subcutaneous adipose tissue in 4.5 years old children. Histogram of fat-signal-fraction of subcutaneous adipose tissue in 4.5 years old children from MRS acquired on the same day as water-fat MRI.