LEP and obesity due to melanocortin 4 receptor deficiency: In fact, several studies have found an association between metabolic programming of obesity and the presence of lower expression levels of leptin (and generally also insulin) receptors in the hypothalamus of these animals, as well as altered signaling of these hormones (Desai et al., 2007a; Breton et al., 2009; Garcia et al., 2010; Palou et al., 2012).