GCG and type 2 diabetes mellitus: In contrast, peptide YY (PYY) and GLP-1 are predominantly released from L-cells in the ileum and in humans distal (190 cm from the pylorus) glucose infusion substantially increased plasma GLP-1 levels, whereas proximal infusion (13 cm beyond the pylorus) had minimal effect on GLP-1 levels in healthy individuals and type 2 diabetic patients [50].