Endogenous Fatty Acid Synthesis Drives Brown Adipose Tissue Involution.

Thermoneutral conditions typical for standard human living environments result in brown adipose tissue (BAT) involution, characterized by decreased mitochondrial mass and increased lipid deposition. Low BAT activity is associated with poor metabolic health, and BAT reactivation may confer therapeutic potential. However, the molecular drivers of this BAT adaptive process in response to thermoneutrality remain enigmatic. Using metabolic and lipidomic approaches, we show that endogenous fatty acid synthesis, regulated by carbohydrate-response element-binding protein (ChREBP), is the central regulator of BAT involution. By transcriptional control of lipogenesis-related enzymes, ChREBP determines the abundance and composition of both storage and membrane lipids known to regulate organelle turnover and function. Notably, ChREBP deficiency and pharmacological inhibition of lipogenesis during thermoneutral adaptation preserved mitochondrial mass and thermogenic capacity of BAT independently of mitochondrial biogenesis. In conclusion, we establish lipogenesis as a potential therapeutic target to prevent loss of BAT thermogenic capacity as seen in adult humans.

Brown Fat-Activating Lipokine 12,13-diHOME in Human Milk Is Associated With Infant Adiposity.

CONTEXT: Little is known about the specific breastmilk components responsible for protective effects on infant obesity. Whether 12,13-dihydroxy-9Z-octadecenoic acid (12,13-diHOME), an oxidized linoleic acid metabolite and activator of brown fat metabolism, is present in human milk, or linked to infant adiposity, is unknown. OBJECTIVE: To examine associations between concentrations of 12,13-diHOME in human milk and infant adiposity. DESIGN: Prospective cohort study from 2015 to 2019, following participants from birth to 6 months of age. SETTING: Academic medical centers. PARTICIPANTS: Volunteer sample of 58 exclusively breastfeeding mother-infant pairs; exclusion criteria included smoking, gestational diabetes, and health conditions with the potential to influence maternal or infant weight gain. MAIN OUTCOME MEASURES: Infant anthropometric measures including weight, length, body mass index (BMI), and body composition at birth and at 1, 3, and 6 months postpartum. RESULTS: We report for the first time that 12,13-diHOME is present in human milk. Higher milk 12,13-diHOME level was associated with increased weight-for-length Z-score at birth (ß = 0.5742, P = 0.0008), lower infant fat mass at 1 month (P = 0.021), and reduced gain in BMI Z-score from 0 to 6 months (ß = -0.3997, P = 0.025). We observed similar associations between infant adiposity and milk abundance of related oxidized linoleic acid metabolites 12,13-Epoxy-9(Z)-octadecenoic acid (12,13-epOME) and 9,10-Dihydroxy-12-octadecenoic acid (9,10-diHOME), and metabolites linked to thermogenesis including succinate and lyso-phosphatidylglycerol 18:0. Milk abundance of 12,13-diHOME was not associated with maternal BMI, but was positively associated with maternal height, milk glucose concentration, and was significantly increased after a bout of moderate exercise. CONCLUSIONS: We report novel associations between milk abundance of 12,13-diHOME and adiposity during infancy.