TGFB1 and atrial fibrillation: In addition, the expression of miR-133 and miR-590 in the atrium of smokers with atrial fibrillation and nicotine-induced atrial fibrillation was down-regulated, and the protein expressions of target genes TGF-β1 and TGF-β RII was up-regulated, resulting in increased collagen production of atrial fibroblasts, which in turn induced atrial fibrosis and atrial fibrillation (Shan et al., 2009).