The mechanisms by which the pathways presented here modulate ceramide content in obesity often remain vaguely defined, and the vast majority of studies report correlative changes in the expression of proteins involved in general ceramide turnover, such as SPT, DES, or CDase, regardless of whether their alteration is the cause or consequence of altered metabolic control. The gene discussed is AGXT; the disease is obesity due to melanocortin 4 receptor deficiency.