IGFBP1 and type 1 diabetes mellitus: To evaluate whether IGFBP1 DNA methylation changes and serum protein levels were dependent on BMI in T1D, we divided all T1D patients into four groups according to BMI (that is, low-weight group (BMI < 18.5 kg/m2), normal-weight group (18.5 to 25.0 kg/m2), overweight group (25.0 to 30.0 kg/m2), and obese group (≥ 30.0 kg/m2).