AQP7 and obesity due to melanocortin 4 receptor deficiency: AQP7-null mice showed accumulation of cellular glycerol, triacylglycerols (TAG) and glycerol kinase up-regulation, which leads to development of progressive adipocyte hypertrophy and early obesity onset (Hara-Chikuma et al., 2005; Hibuse et al., 2005).