GLP1R and obesity due to melanocortin 4 receptor deficiency: Additional mechanisms driven by obesity include gut epithelial lymphocytes sequestering GLP-1, decreased availability of GLP1-secreting enteroendocrine L cells, or lymphocyte-driven upregulation of the expression of molecules (dipeptidyl peptidase 4 (DPP4)) degrading GLP1 [91,463].