OBP2A and obesity due to melanocortin 4 receptor deficiency: While Cho et al (2011) and Sheng et al (2011) observed reduced LCN13 levels both in liver and the circulation in different mouse models of obesity (Cho et al, 2011; Sheng et al, 2011), LCN13 expression was unresponsive to metabolic dysfunction in our hands (Figs 4A, 5B, 6A, and 7A).