XBP1 and obesity due to melanocortin 4 receptor deficiency: Importantly, as a novel regulator of metabolic homeostasis (Lee et al., 2008; Zhou et al., 2011; Wu et al., 2014), the proposed XBP1 regulation of VEGF also broadens our knowledge on the pathologies of metabolic syndrome and sheds light on the intervention of diabetes mellitus and obesity‐related metabolic diseases.