| 研究実績の概要 |
MicroRNA-122 is highly expressed in liver and secreted into blood, which is reported to enter other tissues to modulate lipid metabolism. Brown adipose tissue is responsible for non-shivering thermogenesis required for body temperature maintenance in cold environments. Since BAT activity is deeply related to lipid metabolism, there may be metabolic crosstalk between the liver and BAT through miR-122. In this study, we examined the effect of cold exposure on circulating miR-122 levels in mice. Cold exposure significantly increased the expressions of Uncoupling protein 1, a key molecule for thermogenesis, indicating the activation of BAT. Cold exposure significantly increased cir-miR-122 level but caused no change in the miR-122 levels and its liver precursor. In contrast, cold exposure significantly decreased miR-122 level in muscle, but not in BAT, suggesting that increased cir-miR-122 was due to the enhancement of its secretion from the muscle. To examine whether BAT thermogenesis was a prerequisite for increased cir-miR-122 and decreased miR-122 level in muscle, effect of cold exposure was examined in UCP1-KO mice. While expressions of thermogenesis-related genes in BAT, except for that of Ucp1, was increased after cold exposure, no significant changes were observed in cir-miR-122 and muscle miR-122 level in UCP1-KO mice. These results suggest that cold-induced activation of BAT thermogenesis increased cir-miR-122 through the secretion from muscle.
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| 今後の研究の推進方策 |
In vivo experiments will be done using a murine muscle cell line, C2C12. IL-6, myostatin and 12,13-diHOME at different significant physiological concentrations will be applied to C2C12 differentiated to myocytes. The treatments will be left for 24-48 hours, after which miRNA, RNA and protein from the cells will be recovered for analysis. Media will also be recovered from each treat
ment. MiRNA122 expression (miR122) will be measured from the cell and medium of each treatment.
Two other cell lines: (1) C3H10T1/2, a murine fibroblast cell line, will also be transfected with a miR122 mimic in its differentiated beige adipocyte form and (2) a stable C2C12 cell line transfected with a miR122 inihibitor, will also be used in in vivo experiments. UCP1 expression and other genes upregulated during cold exposure (Fgf21, Dio2, etc) will be measured in transfected
C3H10T1/2. Transfected C2C12 stable cell line will also be treated with IL-6, myostatin and 12,13-diHOME, afterwhich both cell and media will be recovered to be analyzed for genes increased during muscle contraction (shivering).
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