MiR-494-3p regulates mitochondria! biogenesis and thermogenesis through PGC1-α signalling in beige adipocytes

Mitochondria are critical in heat generation in brown and beige adipocytes. Mitochondrial number and function are regulated in response to external stimuli, such as cold exposure and beta 3 adrenergic receptor agonist. However, the molecular mechanisms regulating mitochondrial biogenesis during browning, especially by microRNAs, remain unknown. We investigated the role of miR-494-3p in mitochondrial biogenesis during adipogenesis and browning. Intermittent mild cold exposure of mice induced PPAR gamma coactivatorl-alpha (PGC1-alpha) and mitochondrial TFAM, PDH, and ANT1/2 expression along with uncoupling protein-1(Ucpl) in inguinal white adipose tissue (iWAT). miR-494-3p levels were significantly downregulated in iWAT upon cold exposure (p < 0.05). miR-494-3p overexpression substantially reduced PGC1-alpha. expression and its downstream targets TFAM, PDH and MTCO1 in 3T3Ll white and beige adipocytes (p < 0.05). miR-494-3p inhibition in 3T3-L1 white adipocytes resulted in increased PDH (p < 0.05). PGC1-alpha.,TFAM and Ucpl mRNA levels were robustly downregulated by miR494-3p overexpression in 3T3-L1 beige adipocytes, along with strongly decreased oxygen consumption rate. PGC1-alpha. and Ucpl proteins were downregulated by miR-494-3p in primary beige cells (p < 0.05). Luciferase assays confirmed PGC1-alpha. as a direct gene target of miR-494-3p. Our findings demonstrate that decreased miR-494-3p expression during browning regulates mitochondria! biogenesis and thermogenesis through PGC1-alpha.