RARRES2 and obesity due to melanocortin 4 receptor deficiency: Circulating serum levels of chemerin have been reported around 10–8 mol/L in healthy lean rats and humans (Stejskal et al., 2008; Stelmanska et al., 2013) and increased in pathological conditions, such as diabetes and obesity (Zabel et al., 2005a; Lin et al., 2019).