Altered thiol/disulfide homeostasis in patients with diabetes mellitus and its chronic complications.

To evaluate the effect of diabetes mellitus and its chronic complications on thiol/disulfide homeostasis. The study included 381 participants divided into six groups: healthy controls (Group 1; n = 91), patients with prediabetes (Group 2; n = 50), patients with diabetes mellitus without complications (Group 3; n = 70), patients with diabetic retinopathy (Group 4; n = 47), patients with diabetic nephropathy (Group 5; n = 70), and patients with diabetic foot (Group 6; n = 53). Thiol/disulfide homeostasis was determined by measuring the reduction reaction of oxidized thiols. Native thiol levels were low in patients with diabetes mellitus complications (Group 4, 264.7 ± 58.5 µmol/L; Group 5, 246.6 ± 67.5 µmol/L; Group 6, 174.3 ± 65.9 µmol/L), as were total thiol levels. The highest and lowest disulfide levels were observed in Group 1 (controls; 20.4 ± 5.2 µmol/L) and Group 6 (16.2 ± 5.7 µmol/L), respectively. The disulfide/native thiol ratio was increased in Groups 4, 5, and 6 compared with Groups 1, 2, and 3. The presence of diabetes mellitus complications substantially decreased native thiol, total thiol, and disulfide levels.