UCP1 and obesity due to melanocortin 4 receptor deficiency: Notwithstanding, although its role in shaping the thermogenic adipocyte phenotype remains to be clarified, the hitherto unexplored possibility that HIF1A directly binds to the promoter region and regulates UCP1 gene-expression, may shed new light on the regulation of thermogenicity of adipocytes and provide promising targets for the pharmacological treatment of obesity.