DPP4 and metabolic disease: DPP4 levels have been studied in many non‐communicable pathologies, and abnormal levels have been observed in metabolic disorders (i.e. type II diabetes and metabolic syndrome) 67, 68, auto‐immunity (i.e. multiple sclerosis, rheumatoid arthritis) 56, 69 and cancer (i.e. B‐cell leukaemia, hepatocellular carcinoma, bladder cancer) 61, 70, 71.