miR-494 Regulates Mitochondrial Biogenesis and Thermogenesis through PGC1-α Signaling in Beige Adipocytes
Authors: LEMECHA MENGISTU , MORINO KATSUTARO , IMAMURA TAKESHI , IWASAKI HIROTAKA , OHASHI NATSUKO , YAMAMOTO HIROTAKA , UGI SATOSHI , MAEGAWA HIROSHI 
Published: June 2018

Background: Mitochondria play an essential role in the heat generation in beige adipocytes. Their number and function are regulated in response to external stimuli such as cold exposure and beta-3 adrenergic receptor (β3-AR) agonist. Previously, we have reported that miR-494 regulates mitochondrial biogenesis in the skeletal muscle. However, this remains unknown in beige adipocytes.
Aim: We investigated the role of miR-494 on mitochondrial biogenesis during adipogenesis and browning.
Result: C57BL/6J mice were subjected to intermittent mild cold exposure. The expression levels of peroxisome proliferator activated receptor gamma coactivator 1-alpha (PGC1-α) and mitochondrial proteins including mitochondrial transcription factor A (TFAM), pyruvate dehydrogenase (PDH), mitochondrially encoded cytochrome c oxidase (MTCO1) and uncoupling protein 1 (Ucp1) were strongly increased in inguinal white adipose tissue (iWAT). On the contrary, that of miR-494 resulted in 27% reduction (p &lt; 0.05) in iWAT following 12°C cold exposure for 6 hours. Furthermore, β3-AR stimulation potently reduced miR-494 expression in 3T3-L1 beige cells. Overexpression of miR-494 substantially reduced the protein expression of PGC1-α and its downstream targets such asTFAM and MTCO1 (p &lt; 0.05). In contrast, antisense of miR-494 significantly increased the expression of TFAM, MTCO1 and PDH (p &lt; 0.05). Overexpression of miR-494 strongly decreased the oxygen consumption rate in 3T3-L1 beige cells and protein expression of PGC1-α and Ucp1 (p &lt; 0.05) in primary beige adipocytes. Finally, we explored the direct target of miR-494 and found that 3`UTR region of PGC1-α is a direct target of miR-494 by luciferase assay.
Conclusion: These findings demonstrate that miR-494 directly inhibits the expression of PGC1-α in adipose tissue. The decreased miR-494 expression during adipocyte differentiation removes its inhibitory effect, leading to stimulation of Ucp1 expression and mitochondrial biogenesis.

Disclosure
M. Lemecha: None. K. Morino: Research Support; Self; Astellas Pharma US, Inc., AstraZeneca, Sunstar Inc., CMIC Pharmascience, Kowa Pharmaceutical. T. Imamura: None. H. Iwasaki: None. N. Ohashi: None. H. Yamamoto: None. S. Ugi: Research Support; Self; Boehringer Ingelheim Pharmaceuticals, Inc., MSD K.K. H. Maegawa: Speaker's Bureau; Self; Astellas Pharma US, Inc.. Research Support; Self; Astellas Pharma US, Inc.. Speaker's Bureau; Self; Mitsubishi Tanabe Pharma Corporation. Research Support; Self; Mitsubishi Tanabe Pharma Corporation. Speaker's Bureau; Self; Sanofi. Research Support; Self; Sanofi. Speaker's Bureau; Self; Nippon Boehringer Ingelheim Co. Ltd.. Research Support; Self; Nippon Boehringer Ingelheim Co. Ltd.. Speaker's Bureau; Self; Daiichi Sankyo Company, Limited. Research Support; Self; Daiichi Sankyo Company, Limited, Takeda Pharmaceutical Company. Speaker's Bureau; Self; Takeda Pharmaceutical Company, Novo Nordisk A/S, Eli Lilly and Company.