TCF7L2 and type 2 diabetes mellitus: showed a substantial number of differentially methylated CpG sites between obese and non-obese adolescents (14–20 years old) and associated to gene previously linked to obesity and T2D, such as FTO, glucokinase (GCK), hepatocyte nuclear factor-1 α and β (HNF1A and HNF1B), peroxisome proliferator-activated receptor gamma (PPARγ), phosphatase and tensin homolog (PTEN), and transcription factor 7-like 2 (TCF7L2) (99).