SCD and type 2 diabetes mellitus: Many studies suggest that delta-5-desaturase (D5D) activity (FADS1) is associated with a lower risk of T2D [29], while stearoyl-CoA desaturase 1 (SCD1) [27] and delta-6-desaturase (D6D, FADS2) variants are linked with insulin resistance and worsening of glucose tolerance or an increased risk of T2D [15,29,30,31,32].