The Experimental Study Of The Injury To Human Proximal Tubular Epithelial Cells Induced By Xylitol

Objective:1 To observe the effects of xylitol(Xy) on the ultramicrostructure of the renal tubules in streptozotocin(STZ) induced diabetic rats.2 To observe the expression of monocyte chemoattractant protein-1(MCP-1) and type I collagen(Col-I)in human proximal tubular epithelial cells(HK-2) cultivated with different concentrations of xylitol,glucose and uric acid(UA) and observe if there is any direct injury to renal tubular epithelial cell in order to further evaluate the advantages and disadvantages of Xy as food additives.Method:1 Experiment in vivo:The 100 male Wistar rats were randomly divided into following groups:normal control group(group NC,n=16).Diabetes model was established in the other 84 rats.Then,80 diabetic rats were selected and randomly divided into four groups:diabetes control group(group DC,n=20),5%Xylitol-treated group(group 5%,n=20),10%Xylitol-treated group(group 10%,n=20) and 20%Xylitol-treated group(group 20%,n=20).Diabetes model was established in rats by intravenous injection of STZ at dose of 50 mg·kg^-1.After 72 hours,measured blood glucose,and the one whose blood glucose was above 16.7mmol/L was enlisted. Then,each group rats were executed and choose their left kidney to observe the ultramicrostructure of renal tubules with transmission electron microscope(TEM) at the end of 8 weeks.2 Experiment in vitro:HK-2 cultivated in vitro were randomly divided into following groups:normal control group,different concentrations of Xylitol(1,5,10,20mmol/L),glucose(25,30mmol/L),and UA(0.1,0.2,0.4,0.8 mmol/L);Then,detect the proliferation activity of HK-2 at 24h,48h and 72h respectively with the thiazolyl blue(MTT) method and observe the expression of MCP-1 and Col-I in HK-2 at 48h with the immunocytochemistry method.Results:1 Experiment in vivo①The change of body weight and blood glucose:The body weight were lighter and the blood glucose were higher of all diabetes groups than group NC(P＜0.05).Compared with the group DC,three groups received dietary xylitol supplementation have higher body weight and lower blood glucose,but only the difference of body weight between the group 20%and the group DC was significant(P＜0.05).②The change of the kidney weight index(kiney weight/body weight):The kidney weight index of all diabetes groups were higher than NC group (P＜0.05).Compared with the group DC,group 20%had lower kidney weight index (P＜0.05).③The change of the ultramicrostructure of renal tubules:Compared with the group NC,all diabetes groups were injured apparentely;The group 10%were injured more seriously than the group DC the group 20%;The group 20%were almost similar to the group DC.2 Experiment in vitro①The proliferation activity of HK-2:The difference between all xylitol groups and the group NC was not significant(P＞0.05).At 48h and 72h the OD value decreased with the increasing of the concentrations of glucose,the difference between the group 30mmol/L and the group NC was significant(P＜0.05).At 48h and 72h the OD value decreased with the increasing of the concentrations of uric acid,and the difference between all uric acid groups and the group NC was significant(P＜0.05).②The expression of MCP-1 and Col-I in HK-2:The difference between all xylitol groups and the group NC was not significant(P＞0.05).Compared with the group NC,the expression of MCP-1 and Col-I were significantly increased in group 25mmol/L and 30mmol/L,and the group 30mmol/L were more than the group 25mmol/L(P＜0.05).The expression of MCP-1 and Col-I in kidney were up-regulated with the increasing of the concentrations of uric acid,and the difference between all and the group NC was significant(P＜0.05).Conclusion:1 Xylitol could decrease the level of blood glucose,body weight;10% xylitol could aggravate the the tubular injury;20%xylitol could improve the blood glucose,promote protein synthesis and increase the excretion of uric acid,then the tubular injury could be lightened.2 Xylitol could have no influence to the proliferation of HK-2 and the expression of MCP-1 and Col-I in it.Xylitol may have no direct injury to renal tubular epithelial cell,it could heighten the level of serum uric acid by metabolic pathway in vivo to aggravate the the tubular injury.3 High glucose and high uric acid could inhibit the proliferation of HK-2 and increase the expression of MCP-1 and Col-I in it,they could have direct injury to renal tubular epithelial cell.