UCP1 and obesity due to melanocortin 4 receptor deficiency: Among the five UCP homologs (UCP1–UCP5), UCP2 is the most widely expressed, being involved in thermal regulation in various tissues, including white adipose tissue, liver, kidney, pancreatic islets, macrophages as well as retinal endothelial cells[8,9], and it is thought to play a role in the progress of obesity[10].