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Improvement in depressive symptoms is associated with reduced markers of inflammation and oxidative damage in type 2 diabetic patients

Background and aims: Processes of inflammation and oxidative damage are insufficiently clarified in diabetic patients suffering subsyndromal depression. This study was aimed to examine one-year changes in inflammatory- and pro-oxidative biomarkers in patients who were treated for elevated depressive symptoms that do not reach criteria for clinical depression. Materials and methods: A randomized controlled comparison of two behavioural interventions for subsyndromal depression – six-week lasting psychoeducation and physical exercise, and a control condition consisting of brief diabetes re-education -was performed in the sample of 209 type 2 diabetic patients with subsyndromal depression (aged 57±6 yrs, 54% female, diabetes duration: 11±8 yrs, 32% insulin treated, HbA1c: 7.3%±1.2 and BMI: 30±5 kg/m2). Clinical depression was excluded by using a Structured Clinical Interview for the DSM-IV Axis I disorders. A level of depressive symptoms, endogenous inflammatory markers (leukocytes, CRP), indicators of antioxidative capacity (myeloperoxidase index [MPXI], plasma uric acid), and markers of oxidative damage (sialic acid, urinary 8-OH-deoxyguanosine [u-8- OH-dG] ) were assessed at baseline, and after six-and twelve months. Repeated measures ANOVA’s were employed to determine within- and between-group differences in depressive symptoms and the measured biomarkers at follow- ups. Results: Participants in the psychoeducational- , physical exercise and the control group improved equally in depressive symptoms from baseline to 12-month follow-up (time- versus time x group effect ; F= 12.51 p<.0001 η2=0.07 and F=0.609 p=0.656 η2=0.007 respectively). Total leukocytes significantly decreased in all three groups (7.7±1.8 to 7.1±1.6 F=15.72 p<.0001 η2=.119) as did sialic acid (2.1±0.3 to 1.8±0.3 F=135.67 p<.0001 η2=0.323) and u-8-OH-dG (1.1±0.5 to 0.99±0.5 F=10.66 p<.0001 η2=0.06). No within- and between group changes were registered with respect to CRP and MPXI. Uric acid increased significantly during one year in all three groups (295.1±84.9 to 315.8±84.4 F=12.53 p<.0001 η2=0.07) with time effects being greater in women compared to men (η2=0.13 versus η2=0.03). Conclusion: Lowering depressive symptoms in subsyndromally depressed type 2 diabetic patients was found to be associated with long- term improvements in biomarkers of inflammation and oxidative stress. Treatment of even mild depressive symptoms may have favourable clinical implications.

diabetes; depression; oxidative damage; inflammation

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