The overexpression of fatty-acid synthase (FAS) is obesity-related [29], our data show the expected up-regulation of this protein in HDF mice tissue but, a down regulation in WA and WA-TNF-α spheroids, this finding is related to the fact that the spheroids were not exposed to circulating fat as occurs in animal tissue. Here, FAS is linked to obesity due to melanocortin 4 receptor deficiency.