The Protective Effect And Mechanism Of Rhein On Renal In Obese Diabetic Rats

PARTⅠ: To investigate the protective effect of Rhein on kidneys in obese diabetic rats.Background and objective Diabetic nephropathy(DN) is one of the most common complications of diabetes mellitus(DM), its incidence in DM is 20–40%.It is the leading cause of end-stage renal disease in the west world. The pathophysiological mechanism responsible for DN has not been fully understood yet. There are some important factors such as renal polyalcohol pathway, advanced glycation end products(AGEs), activation of Protein Kinase C,oxidative stress, hexosamine , renal hemodynamic change , many kinds of cytokines and genetic background and so on. Recent studies show that oxidative stress plays a role in the occurrence and development, it was the common physiological and pathological pathway of the diabetic complication of the great vessels and micrangium. Rhubarb and its compound preparation are effective on controlling the symptom of DN and delaying the progress of disease. Rhein as the effective ingredient of Rhubarb has major progress in the research of the treatment of DN. Reseach data demonstrates that Rhein can reduce the urinary albumin, prevent the elevation of SCr, relieve the glomerular sclerosis and improve the glucolipid metabolism. But up to now there is no report whether Rhein has antioxidant function. This experiment aims to confirm the effect of Rhein on glucolipid metabolism and urinary albumin excretion in Obese Diabetic Rats, to observe antioxidation of Rhein on renal, and to investigate the possible mechanism of Rhein preventing and delaying diabetic nephrophy.Methods Male Wistar rats were fed with the diets enriched with sucrose (20%) and lard (10%) and cholesterol (2.5%) and cholic acid (1%).Hyperglycemia was developed by intraperitoneal injection in these rats with 25 mg/kg streptozotocin (STZ) after 8 weeks on the diets.All rats were devided into 5 groups randomly: normal control group (NC),diabetic group(DM), diabetic rats receiving Rhein(DM-RH), diabetic rats receiving Ramipril(DM-RA) and diabetic rats receiving pioglitazone(DM-PI). After administration by gavage for 8 weeks,blood glucose, body weight, blood fat, 24h urinary protein excretion,the content of malondialdehyde (MDA) and superoxide dismutase(SOD) of the cortex renis were measured.Results After modeling the following indexes including blood glucose, body weight, Cholesterol(CHOL),Triglyceride(TG),High density lipoprotein-cholesterol (HDL-C),Low density Lipoprotein Cholesterol (LDL-C) and 24h urinary protein excretion were increased distinctly. After 8 weeks, compared with DM, the glucose of DM-RH and DM-PI was decreased markedly(P < 0.01), the glucose was decreased obviously after the treatment(P <0.01), and the group comparison was no significant difference(P >0.05);CHOL,TG,LDL of DM+RH was lower than DM(P <0.01), but DM-RA and DM-PI not(P >0.05); The 24h urinary protein excretion of DM-RA, DM-PI and DM-RH was obviously lower than DM(P <0.01), DM-RA was superior to DM-PI(P <0.05),but the group comparison between DM-RA and DM-RH was no significant difference(P >0.05).Compared with NC, the level of MDA of DM,DM-RA, DM-PI and DM-RH was increased significantly(P <0.01), the activity of T-SOD was decreased(P <0.01). After the treatment, The level of MDA of DM-RA, DM-PI and DM-RH was increased significantly(P <0.05), the activity of T-SOD was decreased(P <0.05,P <0.01).Conclusion Rhein can control glucose, adjust blood fat, reduce the urinary protein excretion. The antioxidation may be one of the possible mechanisms that Rhein can protect and remitte diabetic nephropathy.PARTⅡ: To investigate the effect of Rhein on the expression of peroxisome proliferators-activated receptors-γ(PPARγ) and transforming growth factor-β1 (TGF-β1) in the cortex renis of the obese diabetic rats.Background and objective Peroxisome proliferators-activated receptors (PPARs) are member of the nuclear receptor superfamily of ligands-dependent transcription factors. These receptors are important to regulate lipid-activated gene transcription, lipid metabolism, inflammation and cell proliferation and differentiation of the cells. and its ligand have been attracted enormous attention due to the key role these receptors play in treatment of DN. Growing laboratorial evidence points to activated PPARγcan reduce the urinary protein and the injury of the nephridial tissue, and inhibit the proliferation of the mesangial cells, the expression of extracellularmatrix secretion and secretion of the inflammatory cytokines. Clinical research demonstrates that PPARγactivator can reduce obviously diabetic urinary protein excretion, urinary protein excretion/creatinine(ACR). TGF-β1 is the kernel factor of the complicate DN cytokine network, and pivotal causative agent due to the renal injury. TGF-β1 has important effects in the pathogenesis of DN such as inducing the proliferation and hypertrophy of the renal cells and stimulating the molecular synthesizing of the ECM. Some research show that activated PPARγcan protect kidney due to reducing the genic expression of TGF-β1, plasminogen activator inhibitor-1 (PAI-1), fibronectin(FN) and typeⅣcollagen. There are different reports about the expression of PPARγin diabetic nephropathy. And there is no report about the effect of Rhein on the PPARγexpression of kidney. In this experiment, we observe the expression of PPARγand TGF-β1 in the cortex renis of the obese diabetic rats, and the effect of Rhein , to reveal the multiplicitas mechanisms that Rhein can protect and remitte diabetic nephropathy.Methods The methods of modeling, diving group, administration, and so on are the same to Part I. We observed that the effect of the Rhein on the expression of PPARγand TGF-β1 in the cortex renis of the obese diabetic rats induced by streptozotocin , high glucos and fat diet with the method of immune histochemistry, RT-PCR and western blot, and investigate the multiple mechanism of the prevention to DN of the Rhein.Results Compared with normal control group, the expression of PPARγin the rats of diabetic group(DM), diabetic rats receiving Rhein(DM-RH) and diabetic rats receiving pioglitazone(DM-PI) were increased markedly(P <0.01,P <0.05).The expression of PPARγin the rats of DM receiving Rhein(DM-RH) and diabetic rats receiving pioglitazone(DM-PI) were increased markedly than those in the rats of diabetic group(DM)(P <0.01,P <0.05).There was no significant difference between DM and diabetic rats receiving Ramipril(DM-RA) (P >0.05). The expression of TGF-β1mRNA of the cortex renis in diabetic group(DM) was increased than those in normal control group(NC)(P <0.01).The expression of TGF-β1mRNA of the cortex renis in diabetic group(DM) was decresed markedly than those in DM+RH, DM+RA and DM+PI(P <0.05).Conclusion Rhein can increase the mRNA and protein expression of PPARγ, and reduce the expression of TGF-β1, Rhein can activate PPARγand reduce the function of TGF-β1. It may be another possible mechanism that Rhein can protect and remitte diabetic nephropathy.