The Antioxidative Effect Of Tripterygium Wilfordii Polyglycoside On Diabetic Rats And Its Protective Mechanism

Background Diabetic nephropathy(DN) is one of the chronic complications of diabetes, and it has become the leading reason of end-stage renal failure in the developed countries. Its basic pathological characteristics are glomerulosderosis, glomerular basement membrane thickening, glomerular sclerosis and renal interstitial fibrosis, whitch eventually lead to renal failure. Currently clinic and research studies have confirmed that morbidity of DN had been significantly increased not only in adults but also in children, so childoon DN has become a serious threat to physical and mental health of children. However, the mechanism of DN is unclear. Recent studies have found that oxidative stress (OS) plays a very important role in the occurrence and development of DN. Tripterygium wilfordii polyglycoside (TWP) is total glycosides extracted from tripterygium wilfordii plant, and its main components are epoxy two terpene lactones. Research shows that TWP can inhibit the cellular and humoral immunity and immune response process from the aspects. In recent years, using TWP in treatment of DN from the angle of immune regulation and anti-inflammatory has gradually become a new treatment method. Li Junhua had reported that TWP has antioxidant effects on intestinal mucosa, but it has not been reported whether TWP has antioxidant effects on renal tissue. Thus, on the basic of OS in pathogenesis of DN, the influence of TWP on the OS in DN rat model was analyzed, and the protection effect of TWP on DN rats renal was tested in this article, in order to seek the possible mechanism of TWP on the renal protection effect of DN rats, and to provide experimental data and theoretical basis for the further development, using and more effective clinical treatment of TWP in DN.Objectives In order to study therapeutic effect of TWP on DN rats through the observation of influence of TWP on DN rat diet, water intake, hair, body weight, mental status and the general condition, blood glucose, creatinine clearance (Ccr)、blood urea nitrogen (BUN), as well as24h urinary albumin excretion rate (UAER)and general biochemical indicators; to observe the effect of TWP on renal pathological changes induced by DN through detecting the level of malondialdehyde (MDA), glutathione peroxidase (GSH-Px) activity, the serum catalase (CAT) activity and the level of serum superoxide oxygen anion CO2-).DN rat model was established in this article in order to provide experimental data and theoretical basis for further development, using and more effective clinical treatment of TWP.Methods Eighty-five SD rats were randomly divided into2groups:normal group (n=12) and model-making group(n=72). Rats in model-making group were administered with streptozotocin(STZ) in a single dose of52mg-kg-1intraperitoneally (ip). Three weeks after successful modeling, the rats were randomly divided into4groups:model control group and TWP(4.5,9.0,18.0mg·kg-1)groups. The rats in TWP (4.5,9.0,18.0mg·kg-1) groups were treated with gavage once a day, for8weeks, and the same volume of drinking water was given to normal control group and model control group.The changes of rats body weight, hair, mental health and so on during the experiment were observed. Two days before the end of the experiment, the rats were set into metabolic cages to collect24h urine in order to detect24hUAER. After the drug using for8weeks, the weight was tested, then the rats were anesthetized with10%chloral hydrate, the blood from the heart was collected and centrifuged to detect creatinine clearance (Ccr) and blood urea nitrogen(BUN). The CAT activity was tested by optical method, the level of serum O2-was tested by colorimetry. And the both kidneys were removed and weighted, and the left kidney cortex was treaded with10%homogenate. The level of MDA was determined by thiobarbituric acid condensation, and glutathione peroxidase (GSH-Px) activity were tested by colorimetry. The right kidney was cut into8m3small pieces, the pieces were formalin-fixed, sliced, then the HE staining was used to observe the pathological changes.Ruslts1. Diabetic nephropathy rats model was successfully established. 2. Effect of TWP on the general situation of DN rats:4weeks after treatment, the spirit, food intake, water intake, urine volume of DN rats in TWP groups (9.0,18.0mg·kg-1) were improved,8weeks after treatment, the above phenomenon gradually returned to normal. Compared with the model group, the hair color were improved, and weight gain as well as spontaneous activity were also significantly improved.3. Effect of TWP on body weight, kidney weight, kidney weight/body weight of DN rats:Compared with normal group, the body weight of model control groups were significantly increased (P<0.01), while the kidney weight, kidney weight/body weight index were significantly decreased (P<0.01).Compared with model control group, the body weight of TWP (9.0,18.0mg·kg-1) groups were significantly decreased (P<0.01), while the kidney weight, kidney weight/body weight index were significantly increased (P<0.01).4. Influence of TWP on the glucose, Ccr, BUN and UAER of DN rats:Compared with normal group, blood glucose, Ccr, BUN and24h UAER of model group groups、24hUAER、BUN were significantly increased (P<0.01). Ccr were significantly declined (P<0.01).Compared with model group groups, blood glucose, BUN and24h UAER of TWP (9.0,18.0mg·kg-1) groups were significantly declined (P <0.01). Ccr were significantly increased (P<0.01)5. The effect of TWP on the serum CAT activity, serum O2-content, renal tissue GSH-Px activity and MDA content in DN rats:Compared with normal group, the activity of serum CAT and GSH-Px in renal cortex in model control group was significantly lower (P<0.01), and the level of serum O2-as well as MDA in the renal cortex were significantly higher (P<0.01); compared with model control group, the activity of serum CAT and GSH-Px in renal cortex in TWP (9.0, 18.0mg·kg-1) groups were significantly higher (P<0.01), and the level of serum O2-as well as MDA in the renal cortex were significantly lower (p<0.01).6. Effect of TWP on kidney pathological changes of DN rats:Compared with normal group,the rats in model control group had glomerular hypertrophy, mesangial cell proliferation and glomerular deformation; compared with control rats, TWP (9.0mg·kg-1and18.0mg·kg-1,ig) could significantly improve the histopathological changes of rats.Conclusions1. TWP (9.0and18.0mg·kg-1) can significantly decrease the BUN, kidney weight/body weight and UAER in DN rats, and increase the Ccr in DN rats, improve histopathological changes,which indicate that TWP has a protective effect on the kidney of DN rats.2.One of the protective mechanisms of TWP on the kidneys of DN rats may be related to the enhancement of serum CAT activities and kidney GSH-Px activities and the decline in serum O2-levels and kidney MDA contents caused by TWP treatment.