GCK and hydrops fetalis: For instance, post-natal HF diet exposure in rats and mice has been associated with differential methylation of the hunger/satiety genes melanocortin 4 receptor (Mc4r), proopiomelanocortin (Pomc), and leptin (Lep) as well as the glycotic enzymes glucokinase (Gck) and pyruvate kinase (Pklr) [3,4,5].