PM20D1 and obesity due to melanocortin 4 receptor deficiency: Another important finding of this study is the demonstration that the metabolic phenotypes of two isogenic mouse strains that naturally exhibit differences in thermogenesis and propensity to obesity can be shifted simply by modulating the expression of Pm20d1. In three previous studies, the levels of Pm20d1 were changed by distinct interventions (Long et al. (Long et al. 2016) (Long et al.(Long et al. 2018) (Simoes et al.(Simoes et al. 2025); however, this has never been performed in strains that, in the baseline, express different levels ofPm20d1.