Improved Effect Of Tribulus Terrestris Extract On Immune Function Of Exercise-related Immunosuppressive Rats And Its Mechanism

PurposeTo investigate the effects of Tribulus terrestris (TT) on immune function inover-trained rats and explore the mechanisms-the role of Glucocorticoid (GC) andGlucocorticoid Receptor (GR).MethodsThirty male SD rats (180to200g body weight) were randomly divided into controlgroup (C, n=10), over-trained group (E, n=10) and over-trained+TT group (E+TT,n=10). After three days of adaptive training, the last two groups were trained on amotor-driven treadmill with a progressively increased load (from5m/min speed,5%slope,30min increased gradually to35m/min,15%slope,120min) for6weeks, sixdays per week.30min before training, E+TT group rats took the medicine (120mg/kgbody weight) by gastric irrigation while the others ingested the same amount of saline.The body weight of the rats were detected every week. After six weeks of training, therats blood were drawn, and the levels of plasma testosterone and corticosterone weremeasure by ELISA and the numbers of CD3+, CD4+, CD8+T cells, natural killing(NK) cells and natural killing T (NKT) cells were detected by Flow Cytometry. Thenthe rats were decapitated to collect liver and spleen and the protein expression of GRin these tissues were determined by Western blot.Results1. Distinct decreases of body weight, testosterone/corticosterone (T/C) ratio, thenumbers of CD3+T cells and NK cells were found in the over-trained ratscompared with that of non-exercise rats, indicating successful establishment ofexercise-related immunosuppression.2. Supplement of TT lead to significant increases of T/C ratio, CD4+/CD8+ratio andthe amounts of CD8+cells, NK cells, NKT cells in the over-trained rats.3. The protein levels of GR in liver and spleen decreased obviously in theover-trained rats, while supplement of TT increased the expression of GR in liverand spleen markblely.4. The level of plasma GC in the over-trained+TT rats was decreased obviously(about50%of over-trained rats).ConclusionThese results indicated that:①Supplement of TT improved the suppressed immunefunction resulted from over-training in rats, including increases of CD4+/CD8+ratioand the amounts of NK, NKT cells.②The improved effect of TT on suppressedimmune function in over-trained rats might be related to the increase of GR in liverand spleen and decrease of plasma GC.