UCP1 and obesity due to melanocortin 4 receptor deficiency: As well, increased Ucp1 protein levels in BAT and scWAT of Crtc2LKO mice were reduced by miR-34a expression, and they were restored by co-expression of miR-34a and Fgf21, confirming our hypothesis that Crtc2-miR-34a axis interferes with Pparα-Fgf21 pathway under HFD-induced obesity and insulin-resistant conditions (Fig. 4c).