Brown adipose tissue (BAT) is a metabolically active fat depot critical for energy homeostasis. This study used advanced mass spectrometry to map how alternate-day fasting (ADF) reshapes BAT's lipid landscape in male mice. Researchers found BAT is normally enriched in very long-chain polyunsaturated fatty acids compared to white fat. During fasting-refeeding cycles, BAT undergoes a striking shift toward more saturated lipids, altered glycolysis and triglyceride synthesis, and spatial redistribution of lipid species—changes less pronounced in white adipose tissue. The mTORC1 signaling pathway was identified as the key mechanistic driver, with genetic inactivation of mTORC1 in BAT blunting these adaptive responses.
