208-LB: Plasma Lipidomics Reveals Sex-Specific Associations with? Brown Adipose Tissue in Asian Children

Brown adipose tissue (BAT) plays a crucial role in lipid metabolism. Activated BAT oxidizes fatty acids from triglycerides in lipid droplets during thermogenesis, increasing energy expenditure. The lipidomic profile of BAT has been primarily studied in animals but little in humans. We sought to identify the plasma lipidomic profile associated with BAT in a thermoneutral condition in 6-year-old children (n=134) in the Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort. LC-MS/MS-based quantification of 480 lipids was performed on plasma samples; %BAT was quantified based on fat-signal-fractions of water-fat-MRI. Associations between plasma lipids and the child's %BAT were investigated using multivariate regression analysis adjusting for sex, ethnicity, and BMI. Sex stratification was applied to investigate the sex-specific lipid signatures of %BAT among the 68 boys and 66 girls. The inverse association between %BAT and BMI was stronger in boys (R2 =0.28) than in girls (R2 =0.07). More lipid signatures of %BAT were observed in boys compared to girls; of 63 unique lipid species significantly associated with %BAT, 12 were associated in both genders, 50 in boys and 11 in girls. In boys, lipid species representing triacylglycerol, cholesteryl ester, acylcarnitine, sphingomyelin, ceramide, hexosylceramides and lysophosphatidylcholine classes showed negative associations with %BAT, whereas several phosphatidylethanolamine lipids displayed positive association with %BAT. In girls, opposite trends in effect sizes (R=-0.44) were, however, observed; several lipids in acylcarnitine, diacylglycerol and sphingolipid classes presented positive association with %BAT, while phosphatidylethanolamine lipids showed negative associations with %BAT. These unique associations between plasma lipid species and BAT in a sex-specific manner provide insights into the different potential lipidomic pathways involved in BAT energy metabolism.