Unfortunately, side effects and the appearance of neutralizing antibodies halted the anti-obesity development of this drug, but further studies revealed that administered CNTF acts through a receptor complex belonging to the IL-6 receptor family that is present not only in the brain, but also in the muscle, liver, and adipose tissue, where CNTF treatment collectively promotes insulin sensitivity and energy expenditure [11]. This evidence concerns the gene CNTF and obesity due to melanocortin 4 receptor deficiency.