RB1 and obesity due to melanocortin 4 receptor deficiency: Further, in RIIβ mice [72], pRb-deficient mice [11]; [73] and in mice overexpressing FOXC2 [74], protection against diet-induced obesity is accompanied by an increased RIα/RIIβ ratio, rendering PKA somewhat more sensitive to cAMP, which is accompanied by an increased occurrence of brown adipocytes in WAT.