ERVW-1 and obesity due to melanocortin 4 receptor deficiency: Moreover, treatment of neuronal cells with the inflammatory molecules TNF-α and IL-6, which are also induced within the metabolic environment of obesity (Dorneles et al., 2016; Kern et al., 2018), activates syncytin-1 gene expression (Antony et al., 2007; Mameli et al., 2007).