Tanycytic annexinA1-containing extracellular vesicles control thermogenesis by orchestrating microglial and neuronal functions.

Obesity, a major global health issue, results from disrupted energy balance driven by chronic hypothalamic inflammation and altered intercellular communication. Among the diverse cells orchestrating this regulation, tanycytes--specialized ependymal cells at the brain-blood interface--have emerged as key modulators, yet the molecular mechanisms by which they influence surrounding cells remain poorly understood. Here, we identify Annexin A1 (ANXA1) as a tanycyte-derived anti-inflammatory signal whose expression, localization, and secretion are dynamically regulated by nutritional state and altered under high-fat diet. During positive energy balance, ANXA1 is secreted in CD9 extracellular vesicles (EV), remodeling hypothalamic networks by altering microglial morphology, synaptic density, and neuronal activation. These EV-mediated effects extend systemically to regulate brown adipose tissue thermogenesis, glucose homeostasis, and overall energy balance. Our findings reveal a previously unrecognized tanycyte-microglia-neuron signaling axis and highlight EV-mediated glial communication as a potential therapeutic target in obesity-associated neuroinflammation.