[Renal protection of Tangke Decoction on rats with diabetes and its effect on the expression of TGF-beta1/Smad4].

Objective: To observe the effect of Tangke Decoction (TD) on the expression of TGF-beta1/Smad4 of rats with early diabetes and to explore the effect and mechanism of TD against the renal injury induced by diabetes.

Methods: SD rats were randomly divided into the normal control group (n = 12), the model group (n = 10), the Chinese herbs prevented group (n =10), the Chinese herbs treated group (n = 10), and the Western medicine control group (n = 10). TD (18 mg/kg) was given by gastrogavage to rats in the Chinese herbs prevented group immediately after successful modeling for 12 weeks, once daily. At the 4th week of successful modeling, rats in the rest 4 groups were administered by gastrogavage. Equal volume of normal saline was given to rats in the model group and the normal control group. Benazepril suspension (1 mg/kg) was administered by gastrogavage to rats in the Western medicine control group for 8 weeks, once daily. TD (18 mg/kg) was given by gastrogavage to rats in the Chinese herbs treated group for 8 weeks, once daily. The body weight, kidney weight, index of kidney weight, fasting blood sugar, 24 h urinary albumin excretion rate were examined after experiment. The pathological changes of the renal tissue were observed by HE staining, Masson staining, and electron microscope. The expression of renal transforming growth factor-beta1, (TGF-beta1) and Smad4 were detected using immunohistochemical assay.

Results: Compared with the normal control group, the body weight of rats decreased significantly; the kidney weight, index of kidney weight, blood sugar, 24 h urinary protein excretion, the urinary albumin excretion rate,TGF-beta1 and Smad4 expression increased significantly in the model group (all P < 0.01). Compared with the model group, the aforesaid indices were improved in each treatment group with statistical difference (P < 0.05, P < 0.01). Compared with the Western medicine control group, the kidney weight, index of kidney weight, blood sugar, 24 h urinary protein excretion, and the urinary albumin excretion rate were obviously improved in the Chinese herbs prevented group (P < 0.01). The renal pathological changes were most obvious in the model group significantly, but they were improved in all treatment groups.

Conclusion: TD could obviously improve the symptoms of diabetes and down-regulate the expression of renal TGF-beta1 and Smad4 of early diabetic nephropathy rats, which suggested that TD had certain preventive effect on early diabetic nephropathy.