NRG4 and obesity due to melanocortin 4 receptor deficiency: NRG4 or ErbB4-induced downregulation led to insulin resistance and hepatic steatosis in high-fat diet-fed mice (Wang et al., 2014; Zeng et al., 2018; Wang et al., 2019a; Zhu et al., 2020), supporting the importance of NRG4-ErbB4 signalling in the prevention of obesity-associated metabolic disturbances.