Mucins, large glycoproteins that require many post-translational modifications, are susceptible to unfolding/misfolding, which can initiate ER stress,17 an important contributor to many chronic diseases such as obesity and obesity-related disorders.19,20 In accordance with these observations, we reported here that HFD increased colon immunolabelling of the central regulator of ER stress because of its role as a major ER chaperone, BiP (immunoglobulin heavy chain binding protein), in WT mice. The gene discussed is HSPA5; the disease is obesity due to melanocortin 4 receptor deficiency.