AHR and obesity due to melanocortin 4 receptor deficiency: The mRNA levels of some genes known to be involved in obesity, lipid and sterol metabolism, and inflammation—many of which contained AHR promoter response elements (REs) (Sun et al. 2004)—were affected by Western diet in B6 and B6.D2 mice: ApoA4 (15.9-fold and 10.2-fold), which is involved in innate immunity and fat localization (Shen et al. 2007), and Hsd3b5 (↓0.03-fold, ↓0.03-fold), a gene associated with hepatic steatosis (Guillen et al. 2009).