RNase P generated tRFSer-GCT promotes fat storage in adipocytes via Adrb2 signaling

tRNA-derived small RNAs (tsRNAs) are emerging regulators of metabolism, but their roles in adipose tissue are not well defined. Here, we profiled tsRNA expression in mouse brown adipose tissue (BAT), gonadal white adipose tissues, and inguinal white adipose tissue (iWAT), revealing depot-specific patterns and a notable enrichment of mitochondrial tRF-5c fragments, especially tRF-1:29-chrM.Ser-GCT (tRF^Ser-GCT), in BAT. tRF^Ser-GCT expression correlated with mitochondrial abundance and increased during adipogenic differentiation and metabolic activation, both in vivo and in vitro. Functionally, tRF^Ser-GCT promoted adipogenesis and lipid accumulation in 3T3-L1 cells and localized to mitochondria. Mechanistically, tRF^Ser-GCT is generated from mitochondrial tRNA^Ser-GCT by the Ribonuclease P complex (Trmt10c, Hsd17b10, Prorp), with Hsd17b10 being essential for its biogenesis and for normal adipocyte lipid metabolism. tRF^Ser-GCT directly targets and downregulates Adrenoceptor Beta 2, a key metabolic regulator. In vivo, restoring tRF^Ser-GCT in Hsd17b10-deficient mice partially rescued adipose tissue accumulation and adipogenic gene expression. Together, these findings identify tRF^Ser-GCT as a mitochondrial tsRNA that promotes adipogenesis via the Ribonuclease P - Adrenoceptor Beta 2 axis, revealing a new layer of tsRNA-mediated regulation in adipose tissue biology.