GPR151 and obesity due to melanocortin 4 receptor deficiency: GPR151 is a critical element of antigen recognition and activation of the immune response,59 60 and PTVs in GPR151 have been reported to have a protective effect against obesity and type 2 diabetes in the UK Biobank.61 In addition, lower levels of bacterial carbohydrate degradation lead to lower carbohydrate absorption in the gut by the host, which pinpoints potential mechanisms by which GPR151 variants can protect against metabolic diseases.