CYP1A1 and obesity due to melanocortin 4 receptor deficiency: There were several other notable DE genes within the top 20 list with relevance to obesity and T2DM, including: DPP4 (dipeptidyl peptidase 4) [35], TNFAIP3 (tumour necrosis factor alpha inducible protein 3), CYP1A1 (cytochrome P450 family 1 subfamily A member 1) and AKR1B1 (aldo-keto reductase family 1 member B).