Merit of Astragalus polysaccharide in the improvement of early diabetic nephropathy with an effect on mRNA expressions of NF-κB and IκB in renal cortex of streptozotoxin-induced diabetic rats

Diabetic nephropathy (DN) is the leading cause of the end-stage failure of kidney, but the efficacy of currently available strategies for the prevention of DN remains poor. An activation of the transcription factor, nuclear factor-kappaB (NF-kappaB), has been suggested to be a key step in the pathogenesis of DN. In the present study, we investigated the effect of Astragalus polysaccharide (APS), an aqueous extract from the Astragalus membranaceus roots, on gene expressions of NF-kappaB and an inhibitory protein of nuclear factor-kappaB (IkappaB) in experimental DN induced by streptozotocin in male Sprague-Dawley rats.Rats with DN were treated with APS (1g/kg p.o.) or benazepril (1.5mg/kg p.o.), an angiotensin-converting enzyme inhibitor, using as positive control. The biochemical parameters such as blood glucose, plasma lipid and microalbuminuria were measured. Also, the mRNA level of NF-kappaB or IkappaB in renal cortex was determined using reverse transcription-polymerase chain reaction.Eight weeks after the treatment, symptoms including shineless, bristly hair, polyuria, polydipsia, lethargy, physical inactivity, loss of body weight, kyphosis and decubitus position were ameliorated by APS. The levels of blood glucose, plasma lipid and microalbuminuria were lowered in APS-treated rats compared with control rats. The ratio of kidney weight over body weight was reduced and the renal function was improved after APS treatment. The mRNA level of NF-kappaB in renal cortex was decreased and IkappaB mRNA expression was raised by APS. These results suggest that APS has prophylactic and therapeutic effects on the progress of DN;therefore, APS is helpful for the prevention and/or treatment of DN at early stage.