Cold-induced Cpt1 repression uncouples lipid mobilization from oxidation and drives lipotoxicity during honeybee...

Reliant on precise nest thermoregulation, the development of stenothermic honeybee brood is highly vulnerable to thermal deviations, which can precipitate severe developmental consequences. While metamorphic prepupae exhibit pronounced chill-susceptibility, the metabolic mechanisms underpinning cold-induced developmental arrest remain elusive. Here, we show that 20 °C cold stress disrupts lipid homeostasis by uncoupling lipid mobilization from mitochondrial β-oxidation. Integrative transcriptomic and metabolomic profiling unveils a "futile mobilization" cycle wherein extensive lipolysis and triglyceride consumption occur, yet the resulting free fatty acids are sequestered from mitochondrial entry. Such pathway obstruction stems from the specific transcriptional repression of Carnitine palmitoyltransferase 1 (Cpt1), the rate-limiting gateway of the carnitine shuttle. The subsequent failure to utilize mobilized lipids drives the maladaptive incorporation of polyunsaturated fatty acids (PUFAs) into membrane phospholipids, sensitizing cellular membranes to reactive oxygen species (ROS) and triggering lethal lipid peroxidation. Crucially, RNAi-mediated knockdown of Cpt1 under optimal temperatures phenocopies this cascade, establishing a mechanistic link between lipid metabolic uncoupling and lipotoxicity as a fundamental constraint on development in the cold.