UCP1 and obesity due to melanocortin 4 receptor deficiency: For example, while transgenic mice that over-express UCP1 from the adipocyte-specific aP2 promoter (aP2-UCP1 mice) are resistant to high fat diet-induced obesity because of the ectopic expression of UCP-1 in WAT, the excessive expression of UCP1 from the transgene also induced BAT atrophy [43].