Objective:To explore the anti-fibrosis effects of Cassia seed on the renal fibrosis in diabetic rats and its possible mechanisms. Method: Seventy rats were randomly divided into model group (n=60) and normal control group (n=10). Fasted for 12 h

the model group rats were left intraperitoneal injected 55 mg·kg-1 of streptozotocin to induce diabetes. Control rats were given equal volume of normal saline. The model-established rats were randomly divided into 5 groups: diabetic model group(NS

4 mL·kg-1)

captopril group (10 mg·kg-1)

low

medium and high dose Cassia seed groups (1

5

10 g·kg-1). After eight weeks of treatment

fasting blood glucose

serum creatine

24 h urine protein (U Pro)

clearance rate of creatine were detected. The morphology was observed

and the mRNA expression of transforming growth factor β1(TGF-β1) and connective tissue growth factor(CTGF) were detected by RT-PCR. The protein expression of Smad3 and Smad6 were detected by western blot. Result: Compared with normal control group

fasting blood glucose

serum creatine

24 h urine protein (U Pro) were significantly increased (P<0.05)

as well as the mRNA expression of TGF-β1 and CTGF and the protein expression of Smad3 were significantly increased (P<0.05)

but clearance rate of creatine and the protein expression of Smad6 were significantly decreased (P<0.05) in diabetic model group. Compared with diabetic model group

there were obvious improvements after the treatment of Cassia seed (P<0.05)

in addition

the renal pathological changes were also improved. Conclusion: Cassia seed has protective effect against the renal fibrosis induced by STZ in rats

the mechanisms may be related to its ability of down-regulating TGF-β1

CTGF and smad3

and up-regulating smad6 in rats.