Aerobic Exercise Improves Aging-Related Renal Fibrosis By Regulation Of Klotho And Mechanism Of Study

Background: Renal fibrosis is a common pathological pathway leading to end-stage renal failure in various chronic kidney disease(CKD).Aging is an important factor in triggering and maintaining renal fibrosis,and with the aggravation of aging problem in China,the incidence of CKD in the elderly is increasing sharply year by year.Klotho,as an anti-aging-related protein,plays an important role in improving renal fibrosis.In addition,a large number of studies have confirmed that aerobic exercise is an effective means to alleviate renal fibrosis,however,the mechanism is not clear.Therefore,experiments were designed to investigate the effects of aerobic exercise on klotho protein and its upstream and downstream signaling pathways to elucidate some of the mechanisms by which aerobic exercise ameliorates renal fibrosis associated with aging.Methods: The 2-month-old SPF-grade male C57BL/6 mice were randomly divided into: young control group(Y)and young exercise group(YE),and 19-month-old mice were randomly divided into: aging control group(A)and aging exercise group(AE).The mice in the exercise group were required to perform aerobic running platform exercise for12 consecutive weeks.The aerobic exercise protocol was: 8 m/min warm-up for 5 min,increasing the speed by 2 m/min every 2 min until 14 m/min and continuing for 30 min,and relaxing for 2 min at the end of 5 m/min for 5 days/week with a slope of 6%.The post-centrifugation serum was used to detect the indexes of kidney function in mice with the kit;HE staining to detect the microstructural changes of kidney tissue;Masson staining to detect the level of renal fibrosis;q PCR to detect the expression level of relevant m RNA;Western-blotting to detect the expression of relevant proteins.Results:(1)In group A,both creatinine(Cr)and urea nitrogen(BUN)levels were significantly higher compared with group Y(P<0.01),and the overall extent of renal tissue lesions was more serious,with vacuolar degeneration and atrophic necrosis in the tubular epithelium and a large amount of collagen deposition,and significantly lower expression of the tubular epithelial marker E-calcium adhesion protein(E-cadherin)and significantly higher expression of the renal injury molecule-1(Kim-1),the renal interstitial marker a-smooth muscle actin(a-SMA)and fibronectin were significantly increased,indicating that aging leads to renal impairment and renal fibrosis;these indices were significantly improved in the AE group after 12 weeks of aerobic exercise intervention compared with group A(P<0.05).(2)Klotho was significantly higher in the YE group(P<0.05)and decreased in the A group(P<0.01)Compared with the Y group;the amount of Klotho was significantly increased in the AE group(P<0.05)compared with the A group.(3)Compared with group Y,the levels of mi R-34 a were significantly increased in group A,the levels of p-P53 upstream of mi R-34 a were significantly increased,and the levels of transforming growth factor-β1(TGF-β1),a key mediator of pro-renal fibrosis that activates p53,were also significantly increased(P<0.05);compared with group A,the expression of mi R-34 a,p-P53,and TGF-β1 in group AE were significantly decreased(P<0.05).(4)The levels of Wnt1,β-catenin and its downstream matrix metalloproteinase 7(Mmp7)were significantly higher in group A compared with group Y(P<0.01);the expressions were significantly lower in group AE compared with group A(P<0.05).(5)The p-Smad3 amount was obviously raised in group A compared with group Y(P<0.01);and the p-Smad3 was obviously decreased in group AE as compared with group A(P<0.05).(6)In renal fibrosis,a pathological vicious feedback loop consisting of TGF-β1 and its upstream and downstream with Klotho was formed,and aerobic exercise broke this pathological loop and improved the renal fibrosis associated with aging.Conclusion:(1)Aerobic exercise may effectively ameliorate aging-related renal fibrosis by repressing the TGF-β1/p53/mi R34 a signaling route activation,thereby increasing Klotho expression,which in turn inhibits its downstream pro-fibrotic Wnt/β-catenin and TGF-β1/smad3 signaling pathways.(2)Aerobic exercise broke the pathological positive feedback loop formed by TGF-β1 and its upstream and downstream with Klotho,forming a benign feedback loop that delayed renal fibrosis and improved aging-related renal fibrosis.