ERVW-1 and obesity due to melanocortin 4 receptor deficiency: Given that syncytin-1 has key role in myogenesis (Frese et al., 2015), a process that is impaired in humans with obesity (Akhmedov and Berdeaux, 2013), investigating the expression of syncytin-1 in muscle of humans with increased BMI may provide novel insights into the development of sarcopenia in such individuals.