A number of potential anti-diabetic plants were identified through an ethnobotanical survey of the traditional pharmacopeia of the Cree of Eeyou Istchee (CEI-Northeastern Canada) used against symptoms of diabetes and their biological activity assessed by in vitro bioassays. Among these, Sorbus decora C.K.Schneid. (Rosacea) ranked highly and increased the transport of glucose in skeletal muscle cells in culture. The present study thus aimed at confirming the antidiabetic potential of S. decora in in vivo models of insulin resistance and diabetes, notably the streptozotocin Type 1 diabetic rat (STZ), the genetic KK-A(y) Type 2 diabetic mouse and the rat rendered insulin resistant with 10% glucose water consumption for 6 weeks. Sorbus decora ethanol extract (SDEE) was administered orally (200 mg kg(-1)) and compared to metformin (150 or 500 mg kg(-1)). The intragastric (i.g.) gavage of SDEE transiently decreased glycemia in STZ rats in a bi-phasic manner but the effect was cumulative over several days. In KK-Ay mice, SDEE incorporated in food (0.12%) decreased glycemia by 15% within 1 week as compared to vehicle controls. In pre-diabetic insulin-resistant rats, SDEE fed daily by i.g. gavage for 2 weeks significantly decreased the slight hyperglycemia and hyperinsulinemia, without affecting sugar water intake. Using the HOMA insulin resistance parameter, the effect of SDEE was equivalent to that of metformin. In conclusion, the ethanol extract of S. decora demonstrates both anti-hyperglycemic and insulin-sensitizing activity in vivo, thereby confirming anti-diabetic potential and validating CEI traditional medicine.
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