Effects of Differently Processed Rehmannia Roots on Dexamethasone-induced Side Effects in Rats

Background: There are three differently processed rehmannia roots, namely fresh, dried and steamed rehmannia roots (FRR, DRR and SRR), which have different indications according to the theory of traditional Chinese medicine (TCM).Objective: To confirm the effects of different rehmannia roots on dexamethasone (Dex) treatment induced side effects, which belong to Yin Deficiency Syndrome in TCM.Materials and Methods: Rats were subcutaneously injected with Dex (0.1m g/kg) and orally administrated with different roots (2.16 g/kg) for 28 days, with metformin (Met, 0.25 g/kg) as a reference substance. Food intake, blood cell count, and organ weight were recorded, and hepatic glycogen and serum insulin, glucose, free fatty acids, total cholesterol, and malondialdehyde contents wereassayed.Results: Dex treatment led to decreases in food intake, white blood cell count, and spleen index, and increases in hemocrit, heart and liver indexes, hepatic glycogen, and serum contents of insulin, glucose, free fatty acids, total cholesterol, and malondialdehyde. The alterations in food intake, spleen index, hematocrit and serum insulin were significantly relieved by FRR but not DRR and SRR; and on the contrary, heart index was significantly reduced by DRR and SRR but not FRR.Conclusions: Dex treatment results in insulin resistance, high blood viscosity, oxidative damage and immunosuppression in rats, and FRR is better than DRR and SRR in attenuating Dex-induced insulin resistance and high blood viscosity. These findings have thus firstly provided evidence that postharvest processing has a profound influence on the biological activities of Rehmannia roots.