Metabolic factors-triggered inflammatory response drives antidepressant effects of exercise in CUMS rats

Chronic stress is a potential contributing factor for depression, accompanying with metabolic and inflammatory response. Exercise is considered as a treatment for depression, but mechanisms underlying its beneficial effects still remain unknown. The objectives of present study were to confirm that metabolic factors-triggered inflammatory response mediates the antidepressant actions of exercise in chronic unpredictable mild stress (CUMS) rats. It has been found that CUMS stimulated expression of ghrelin and its receptor Ghsr, but inhibited expression of leptin and its receptor LepRb. Ghrelin, via binding to Ghsr, induced phosphorylation of GSK-3β on Tyr216 and decreased phosphorylation on Ser9, thus increasing GSK-3β activity. Conversely, ghrelin binding to Ghsr decreased STAT3 activity, through decreasing phosphorylation of STAT3 on Tyr705 and increasing Ser727 phosphorylation. Negatively correlated with ghrelin, leptin binding to LepRb had opposite effects on the activity of GSK-3β and STAT3 via phosphorylation. In addition, decreased leptin level initiated NLRP3 activity via LepRb. Furthermore, GSK-3β inhibited STAT3 activation, thus promoting the expression of NLRP3. Meanwhile, swim improved metabolic and inflammatory response both in CUMS and control rats. Our findings suggest that exercise not only ameliorates metabolic disturbance and inflammatory response in depression, but also contributes to metabolic and inflammatory function in normal conditions.