miR-21a-5p promoted BPA-induced obesity in vivo while BPA-induced preadipocyte differentiation is repressed by miR-21a-5p by targeting map2k3 in the MKK3/p38/mitogen-activated protein kinase (MAPK) pathway [67]. This evidence concerns the gene MAP2K3 and obesity due to melanocortin 4 receptor deficiency.