| ObjectiveThe Ubiquitin-proteasome system is principal degration route of intracellular and oxidized proteins, thus diabetes-induced oxidative stress can lead to protein misfolding and degradation by the ubiquitin-proteasome system. The aim of this study was to evaluate the activity of ubiquitin-proteasome system in renal tissues of type 2 diabetic rats in relation to inflammation and its renal structural lesions, and to observe the effecs of Pioglitazone, Danshen dripping pill and Quercetin on the renal expression of ubiquitin and NF-κB p65 and to investigate its renoprotective effects.MethodAfter breed adaptively for 1 week, a total of 52 specific pathogen-free male SD rats were randomly divided into 2 groups:normal group for comparison purpose ( group NC, n=8 ) was fed for regular diet and experimental model group ( n=44 ) was fed with fat enriched diets.The rats of experimental model groups were intraperitoneally given low-dose streptozotocin ( STZ, 30 mg/kg ) after having the sucrose and fat enriched diets for 4 weeks. After 72 hours, measured randomly blood glucose twice and the one whose blood glucose was equal or above 16.7mmo1/L was enlisted. The modeling rats were further randomly divided into four groups: type 2 diabetic group ( Group DM, n=9 ) , pioglitazone group ( Group PIO, n=9, 4 mg·kg-1·d-1 ) , danshen dripping pill group ( Group DSP, n=9, 500 mg·kg-1·d-1 ) and quercetin group ( Group QUE, n=9, 100 mg·kg-1·d-1). The rats of treatmental group were performed by intragastric administration for 8 weeks. The rats of two control groups were performed by intragastric administration with equivalent distilled water for 8 weeks. Before the rats were sacrificed, we collected 24 hours urine for measurement of 24h urinary protein, then killed the rats, gathered blood from vein immediately, and measured their fasting plasma glucose, fasting serum insulin, serum creatinine, blood urea nitrogen, triglyceride, total cholesterol, low density lipoprotein cholesterol and high density lipoprotein cholesterol.After that, the kidneys were removed and weighed to calculate the ratio of kidney weight vs body weight ( KW/BW ) . Put the kidney into 10% formalin to be fixed and made paraffinslices. Observed the pathological changes of the kidney and studied the expression of ubiquitin and NF-κB p65 in the kidney with immunohistochemical and Western-blot . The data were analyzed by SPSS13.0 system.ResultsThe features of renal involvement in the model included overt persistent proteinuria and typical morphological changes, Histologically the earliest abnormality was mainly glomerular hypertrophy, Vascular changes, mild mesangial expansion and vacuolation of tubularelinal cell were came forth at the end of exprement.Compared with group NC, the level of fasting plasma glucose, fasting serum insulin, triglyceride, total cholesterol, low density lipoprotein cholesterol, serum creatinine, blood urea nitrogen, 24h urinary protein, the ratio of kidney weight to body weight ( KW/BW ), extracellular matrix accumulation index and the expressions of ubiquitin and NF-κB p65 in type 2 diabetic rats were significantly increased ( P﹤0.01 ), the level of high density lipoprotein cholesterol in group DM was decrease( P﹤0.05 ).Compared with group DM, the level of fasting plasma glucose, fasting serum insulin, triglyceride, total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol, serum creatinine, blood urea nitrogen, 24h urinary protein, the ratio of kidney weight to body weight ( KW/BW ), extracellular matrix accumulation index and the expressions of ubiquitin and NF-κB p65 in group PIO, DSP and QUE were significantly decrease( P﹤0.01 ). the level of high density lipoprotein cholesterol in group PIO, DSP and QUE was no significant difference with group DM( P﹥0.05 ). Afer treamwnt, each index was improved, but not reversed to normal level. It has no significant difference between group PIO, DSPand QUE (P﹥0.05).The expression of ubiquitin and NF-κB p65 were positively related with the level of 24h urinary protein and extracellular matrix accumulation index.Conclusion①The features of renal involvement in the type 2 diabetic rats included overt persistent proteinuria and typical morphological changes. Increasing expression of ubiquitin and NF-κB p65 in type 2 diabetic rats were positively related with functional and pathological damage in rats renal.②Pioglitazone, danshen dripping pill and quercetin can improve glucolipid metabolism, reduce oxidative stress and decrease the expression of ubiquitin and NF-κB p65 in renal tissues of type 2 diabetic rats. Thus they exerts the actions against inflammatory response and to decrease 24h urinary protein, which may have benefit in diabetic nephropathy.
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