RBL1 and obesity due to melanocortin 4 receptor deficiency: Alternatively, reduced proliferation is suggested by upregulation of Cdkn1a/p21 in Camk2n1−/− EAT, which has been shown elsewhere to prevent obesity and adipocyte hyperplasia,37 and downregulation of Rbl1/p107 and Cdk1 that have been shown by others to be pro-obesogenic and upregulated in obesity.38 Furthermore, upregulation of Id3 and downregulation of C1s and C4 provide additional mechanisms for reduced adiponectin production,39 reduced adiposity, and increased insulin sensitivity.32,40