APOB and obesity due to melanocortin 4 receptor deficiency: On the other hand, genes described as "not expressed", including obr,SREBP1, apoB,CCK,CCKR,IGF2 and lipoprotein (APOVLDLII), which have been studied extensively in other species (mainly Homo sapiens and Mus) and shown to affect obesity, were not detected in chicken adipose tissue in the present study.