IL4 and obesity due to melanocortin 4 receptor deficiency: IL-4 regulates lipid metabolism (143), and (142) recent findings highlight an intriguing relationship between non-hematopoietic IL-4Rα activation of a non-canonical signaling pathway that regulates a high-fat, high-carbohydrate diet-driven induction of obesity and impacts the severity of obesity-associated sequelae in mice (212).