ATF3 and obesity due to melanocortin 4 receptor deficiency: Jiang et al. demonstrated that hypoxia or ATF3 overexpression impaired mitochondrial function in differentiated 3T3-L1 fibroblast-like cells, and ATF3 deletion partially recovered hypoxia-mediated mitochondrial dysfunction, suggesting that ATF3 may play a role in adipocyte hypoxia-mediated mitochondrial dysfunction in obesity (39).