INS and type 2 diabetes mellitus: While there was no significant difference in FPG/HbA1c levels between T2DM patients in this study with or without metformin treatment, the metformin-treated T2DM patients had significantly higher circulating insulin and C-peptide levels than both non-treated T2DM patients and healthy controls (Supplementary Table S1) suggesting that these T2DM patients had a more severe form of insulin resistant T2DM.