Tubulointerstitial damage is a crucial therapeutic target in preventing chronic kidney disease (CKD) progression. Inappropriately activated renin–angiotensin–aldosterone system (RAAS) in the tubulointerstitial area is strongly associated with tubulointerstitial damage progression. Therefore, this study aimed to determine whether there is a beneficial effect of voluntary running exercise training on aldosterone-induced renal injury. Human L-type fatty acid-binding protein (L-FABP) chromosomal transgenic (L-FABP+/−) male mice were used to evaluate the effect of exercise by using urinary L-FABP, a tubular marker. The mice were assigned to either the exercise group that performed voluntary running exercise training using a running wheel or the control group. Subsequently, two groups were injected with aldosterone (0.125 μg kg−1 min−1) and administered 1% NaCl water, and two groups were administered aldosterone only in solvent 4 weeks after initiating the exercise. Aldosterone was injected for another 4 weeks, and NaCl water was administered from 5 weeks after starting the exercise until 8 weeks. Although both aldosterone and NaCl water significantly decreased the running distance, tubulointerstitial damage involving interstitial infiltration of macrophages and fibrosis and the elevation of urinary human L-FABP induced by aldosterone injection was prevented by voluntary running exercise training. Urinary human L-FABP levels were significantly correlated with the degree of tubulointerstitial damage. In conclusion, voluntary running exercise training delayed tubulointerstitial damage progression in the aldosterone-induced renal injury model and therefore may be a promising nonpharmacological strategy in CKD.
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