Objectives: To study associations of established cardiovascular risk factors, inflammation and carotid artery intima-media thickness (CIMT) with oxidative stress in type 2 diabetes mellitus (T2DM).
Methods: We recruited 343 T2DM subjects from the three main ethnic groups in Singapore (Chinese: 196, Indians: 106, Malays: 41; Age: 54.7±10.4 years; Males: 46%). Measurements: Demographics, BMI, blood pressure, HbA1c, glucose and lipids; CIMT and C-reactive protein (hsCRP). Derivatives of reactive oxygen metabolites (dROMS) and total anti-oxidant status (TAC) was estimated by the automated clinical chemistry analyser (Diacron, Italy). The total oxidative index (OXY) was calculated as the difference between standardised dROMS and TAC values. The relationship between OXY, dROMS and TAC as dependent variable and age, gender, ethnicity, BMI, blood pressure, HbA1c, fasting lipids, log CRP and CIMT as co-variates was assessed using multiple regression analysis. Associations with gender and ethnicity were assessed by student’s t test and Kruskal Wallis test respectively.
Results: The mean OXY was higher in the females (0.2±1.3) compared to the males (0.2±1.0); p<0.001 and highest in the Indians (0.3±1.2) when compared to Chinese (-0.1±1.2) and Malays (-0.1±1.0); p=0.01. OXY exhibited a linear relationship with HbA1c (β=0.09, p=0.01), Non-HDL cholesterol ((β=0.28, p<0.001) and CRP (β=0.21, p<0.001). dROMS associated with HbA1c (β=5.3, p=0.04) and CRP (β=14.80, p<0.001) and TAC associated inversely with non-HDL-cholesterol (β= -121.4, p<0.001). No association with CIMT was seen.
Conclusions: In T2DM, total oxidative stress is a function of HbA1c, non-HDL-Cholesterol and low-grade inflammation. HbA1c and inflammation increase reactive oxygen metabolites, whereas non-HDL cholesterol decreases the anti-oxidant potential. The mechanisms of oxidative stress generation, in particular in various ethnic groups, needs to be studied further.
R. Dalan: None. L. Goh: None. X. Tang: None. D.E.K. Chew: None. B. Boehm: None.