As human AQP7 gene is localized in a chromosomal region with reported linkage to type 2 diabetes (T2D) (Luo et al., 2001; Lindgren et al., 2002) and the metabolic syndrome (Loos et al., 2003), AQP7 expression has been particularly studied in patients suffering from obesity, T2D and metabolic syndrome. This evidence concerns the gene AQP7 and obesity due to melanocortin 4 receptor deficiency.