Serum Markers of Oxidative Stress to Assess Mortality Risk in Patients with Type 2 Diabetes
By Aly Becraft, MS and Kevin C Maki, PhD
Hyperglycemia is thought to result in increased reactive oxygen species (ROS) production and weakened antioxidant capacity,1 which can make patients with type 2 diabetes (T2D) susceptible to elevated oxidative stress. Current research relating diabetes complications and oxidative stress is lacking because ROS are difficult to measure directly;2 however, methods that indirectly quantify oxidative stress by measuring derivatives of reactive oxygen metabolites (d-ROMs) as a proxy for ROS production3 and total thiol levels (TTLs) as a proxy for reduction-oxidation (redox) status of blood4 are also available.
Xuan et al. recently published pooled results from two cohort studies in a meta-analysis to investigate the association of these oxidative stress biomarkers with incident major cardiovascular events, total cancer incidence, and cause-specific and all-cause mortality in patients with T2D.5 Diabetes sub-cohorts of the ESTHER and DIANA studies, conducted in Germany, were included. In the ongoing ESTHER cohort, to date, patient follow up visits have been conducted after 2, 5, 8, 11 and 14 years. Follow up in the DIANA study occurred after 4 and 7 years. For this meta-analysis, the 8-year follow-up data from the ESTHER cohort was used as baseline and the 11-year follow-up for repeated biomarker measurements. For the DIANA study, baseline and the 4-year follow-up data were used. Biomarker measurements were conducted on 1029 patients from the ESTHER cohort, of which 720 had repeated measurements. In the DIANA study, measurements of both biomarkers were performed for 1096 baseline study participants, and repeated measurement of d-ROMs was done for 738 participants.
In both cohorts, significantly increased d-ROMs levels were observed in females, current smokers, patients with T2D who had body mass index (BMI) ≥40 kg/m2, those not taking any antidiabetic medication, with insulin therapy, without lipid-lowering medication, with high total cholesterol levels, or with high C-reactive protein (CRP) levels. In addition, significantly lower TTLs in both cohorts were observed in females, alcohol abstainers, and patients with T2DM with BMI ≥40 kg/m2, without any antidiabetic medication, with insulin therapy, with antihypertensive therapy, with anticoagulant medication, with high CRP levels, with estimated glomerular filtration rate (eGFR), or with a history of myocardial infarction, heart failure, or hypertension. Both biomarkers were significantly associated with all-cause mortality in each of the cohorts; however, the associations with cancer mortality and major cardiovascular events were not statistically significant. Adjustment for disease and CRP concentration attenuated observed effect estimates. Subgroup analysis of all-cause mortality demonstrated strong associations with d-ROM levels among males and among patients with T2D with glycated hemoglobin <7%, age <70 years, BMI <30 kg/m2, and a history of coronary heart disease.
The results of this study support the notion that an imbalanced redox system may play a role in increasing premature mortality in patients with T2D. Other evidence supports such a role for oxidative stress,6-8 but it remains to be determined if oxidative stress is also involved in the development of cardiovascular disease and cancer in patients with T2D. Although this study was observational, and thus, the possibility of residual confounding cannot be disregarded, the results demonstrate the potential need for oxidative stress interventions in patients with T2D and illustrate the usefulness of using d-ROMs and TTLs as biomarkers to identify individuals with T2D who may be at increased risk for premature death.
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