PDE4D and obesity due to melanocortin 4 receptor deficiency: Interestingly, PDE4D level was not changed in patients with obesity, steatosis, or steatohepatitis (Figure 1, F and G) or in obese (ob/ob) mice (Supplemental Figure 1, D–F) but was increased in the human cirrhotic liver (Figure 1, F and H) (37) and correlated with the levels of COL1A1 mRNA (Figure 1I and Supplemental Figure 1G).