Pro-inflammatory cytokines as predictors of antidepressant effects of exercise in major depressive disorder.

Exercise is an efficacious treatment for major depressive disorder (MDD) and has independently been shown to have anti-inflammatory effects in non-depressed subjects. Patients with MDD have elevated inflammatory cytokines but it is not known if exercise affects inflammation in MDD patients and whether these changes are clinically relevant. In the TReatment with Exercise Augmentation for Depression (TREAD) study, participants who were partial responders to a selective serotonin reuptake inhibitor were randomized to receive one of two doses of exercise: 16 kilocalories per kilogram of body weight per week (KKW), or 4 KKW for 12 weeks. Blood samples were collected before initiation and again at the end of the 12-week exercise intervention. Serum was analyzed using a multiplexed ELISA for interferon-γ (IFN-γ), interleukin-1ß (IL-1ß), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Higher baseline levels of TNF-α were associated with greater decrease in depression symptoms over the 12-week exercise period (P<0.0001). In addition, a significant positive correlation between change in IL-1ß and change in depression symptom scores was observed (P=0.04). There were no significant changes in mean level of any cytokine following the 12-week intervention, and no significant relationship between exercise dose and change in mean cytokine level. Results suggest that high TNF-α may differentially predict better outcomes with exercise treatment as opposed to antidepressant medications for which high TNF-α is linked to poor response. Our results also confirm findings from studies of antidepressant medications that tie decreasing IL-1ß to positive depression treatment outcomes.

IL-1ß and BDNF are associated with improvement in hypersomnia but not insomnia following exercise in major depressive disorder.

Given the role of sleep in the development and treatment of major depressive disorder (MDD), it is becoming increasingly clear that elucidation of the biological mechanisms underlying sleep disturbances in MDD is crucial to improve treatment outcomes. Sleep disturbances are varied and can present as insomnia and/or hypersomnia. Though research has examined the biological underpinnings of insomnia in MDD, little is known about the role of biomarkers in hypersomnia associated with MDD. This paper examines biomarkers associated with changes in hypersomnia and insomnia and as predictors of improvements in sleep quality following exercise augmentation in persons with MDD. Subjects with non-remitted MDD were randomized to augmentation with one of two doses of aerobic exercise: 16 kilocalories per kilogram of body weight per week (KKW) or 4 KKW for 12 weeks. The four sleep-related items on the clinician-rated Inventory of Depressive Symptomatology (sleep onset insomnia, mid-nocturnal insomnia, early morning insomnia and hypersomnia) assessed self-reported sleep quality. Inflammatory cytokines (tumor necrosis factor-alpha, interleukin (IL)-1ß, IL-6) and brain-derived neurotrophic factor (BDNF) were assessed in blood samples collected before and following the 12-week intervention. Reduction in hypersomnia was correlated with reductions in BDNF (ρ = 0.26, P = 0.029) and IL-1ß (ρ = 0.37, P = 0.002). Changes in these biomarkers were not associated with changes in insomnia; however, lower baseline levels of IL-1ß were predictive of greater improvements in insomnia (F = 3.87, P = 0.050). In conclusion, improvement in hypersomnia is related to reductions in inflammatory markers and BDNF in persons with non-remitted MDD. Distinct biological mechanisms may explain reductions in insomnia.