Abstract

Dexamethasone is an anti-inflammatory glucocorticoid that may alter glucose and lipid homeostasis depending on the dose and/or duration of administration. Nigella sativa oil (NSO) can be used as potential modulator of intermediary glucose and lipid metabolism. Herein, the authors evaluated the dose-dependent effects of NSO (0.2 and 0.4 ml/kg body weight) supplementation on plasma glucose, insulin and triglyceride concentration in rats treated with dexamethasone (1 mg/kg body weight) for 5 days. Adult male Wistar rats (150 to 200 g) were housed and treated in the animal holding facility of the Faculty of Basic Medical Sciences, University of Ilorin, Ilorin. Animals were randomly distributed into 4 groups: control (normal saline, 1 ml/kg), DEX (dexamethasone 1 mg/kg), DEX + NSO 0.2 ml/kg and DEX+ NSO 0.4 ml/kg. All drugs were administered intraperitoneally. To assess insulin resistance, an insulin tolerance test was performed in addition to fasting glucose and insulin measurements used in calculating the homeostatic model assessment of insulin resistance index (HOMA-IR). Insulin-induced glucose lowering was improved following NSO supplementation during the insulin tolerance test (p<0.05). Likewise, there was a reduction in fasting hyperinsulinemia (50%; p<0.05) and HOMA-IR index. Dexamethasone induced hypertriglyceridemia which was not significantly reduced following NSO supplementation. Furthermore, NSO had no significant effect on liver alanine aminotransferase enzyme activity in rats treated with dexamethasone. In conclusion, it is shown that 5 days therapy with dexamethasone can be used as a model of insulin resistance and NSO supplementation for 5 consecutive days attenuates hyperglycemia and insulin resistance induced by dexamethasone treatment.

Key word: Dexamethasone, insulin resistance, Nigella sativa oil.