Since expression of TGF-β1 is positively correlated with obesity and TGF-β1 transmits its signals via the transcriptional factor Smad3 (23), we examined the effect of treatment with the miR mimic on the TGF-β/Smad3 signaling pathway during obesity. This evidence concerns the gene SMAD3 and obesity due to melanocortin 4 receptor deficiency.