MTHFR and diabetes mellitus: In the context of diabetes complications, while the hypermethylated MTHFR profile has been associated with DR (Nunes et al., 2017), in the DN, the results are contradictory, because while hypermethylation predominated in patients with end-stage renal disease (Ghattas et al., 2014), diabetics with initial DN or in less advanced stages had a higher occurrence of the non-methylated profile (Yang et al., 2016; Nunes et al., 2017).