Twelve-week Intervention Comparing High- And Low-intensity Exercise To Waitlist Control (n = 113) On IGF-1 In MDD

Insulin-like growth factor-1 (IGF-1) is typically higher in major depressive disorder (MDD) and possibly related to neurocognitive dysfunction. Acute exercise acutely increases serum IGF-1, however little is known about the effects of chronic exercise training. Through repeated, acute exercise-induced IGF-1 increases (e.g., exercise training) in MDD, the IGF-1 system may be regulated, leading to lowered depressive symptoms. PURPOSE: To determine the effects of high-intensity (HEX) or low-intensity (LEX) exercise on changes in resting serum IGF-1 compared to waitlist (WL). METHODS: Data was collected from adults with MDD in Germany (ages 18-65; n = 113) before and after a 12-week exercise intervention. Participants were randomly assigned to HEX (n = 41), LEX (n = 42) or WL (n = 30). Aerobic exercise sessions occurred twice weekly for 60 min/session. Demographics, resting serum IGF-1, and depressive symptoms (Hamilton Rating Scale for Depression; HAMD), were collected at baseline and post-intervention. Linear regressions modeled associations between IGF-1 and HAMD across time and group assignment. Linear trend analysis was performed to evaluate a potential dose-response effect on changes across time and Cohen’s d effect sizes were calculated. RESULTS: Being assigned to an exercise group, regardless of intensity, was significantly related to post-intervention IGF-1 levels compared to WL (p < 0.05) with a moderate mean difference (d = -0.59). Being in either the LEX (p < 0.01) or HEX (p < 0.01) groups was significantly, moderately, associated with post-intervention serum IGF-1 (d = -0.61, -0.56, respectively). There was a significant negative linear trend across exercise intensity groups for change in IGF-1 (p < 0.05). Change in HAMD score was not significantly related to change in IGF-1 following the interventions (p > 0.05). CONCLUSIONS: Exercise training regulates IGF-1 by decreasing resting IGF-1 in individuals with MDD and potentially in a dose-response manner with exercise intensity. Changes in serum IGF-1 alone were not associated with changes in depression severity, however IGF-1 may work in conjunction with other exercise-related biological systems to reduce depressive symptoms. Supported by: This work was supported by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG, grant HE7464/2-1). Work by SK and JM was partially supported by NIMH grant #1R61MH129407-01A1.