PurposeTo assess the plasma oxysterol species 7-ketocholesterol (7-Kchol) and cholestane-3,5,6-triol (chol-triol) as biomarkers of oxidative stress in type 1 and type 2 diabetes mellitus (DM).MethodsIn total, 26 type 1 and 80 type 2 diabetes patients, along with 205 age- and gender-matched healthy controls, were included in this study. Oxysterols were quantified by liquid chromatography coupled with tandem mass spectrometry and N,N-dimethylglycine derivatization. Correlations between oxysterols and clinical/biochemical characteristics of the diabetes patients, and factors affecting 7-Kchol and chol-triol, were also determined.ResultsPlasma 7-Kchol and chol-triol levels were significantly higher in type 1 and type 2 diabetes patients compared to healthy controls (P<0.001). Significant positive correlations were observed between oxysterol levels and levels of glycated hemoglobin (HbA1c), glucose, serum total cholesterol, low-density lipoprotein, very-low-density lipoprotein, and triglycerides, as well as the number of coronary risk factors. Statins, oral hypoglycemic agents, and antihypertensive agents reduced the levels of oxysterols in type 2 diabetes patients. Statin use, HbA1c levels, and the number of coronary risk factors accounted for 98.8% of the changes in 7-Kchol levels, and total cholesterol, smoking status, and the number of coronary risk factors accounted for 77.3% of the changes in chol-triol levels in type 2 diabetes patients.ConclusionsPlasma oxysterol levels in DM, and particularly type 2 DM, may yield complementary information regarding oxidative stress for the clinical follow-up of diabetes patients, especially those with coronary risk factors.