Mechanisms of the hypoglycaemic and immunopotentiating effects of Nigella sativa L. oil in streptozotocin-induced diabetic hamsters.

ABSTRACT

The aim of this study was to elucidate the mechanisms underlying the hypoglycaemic effect of N. sativa oil (Nigella sativa oil) in streptozotocin (STZ)-induced diabetic hamsters, in terms of hepatic glucose production, and to investigate the possible immunopotentiating effect of N. sativa oil on peritoneal macrophages. Diabetes was induced by intraperitoneal injection of 65 mg/kg body weight of STZ. Treatment with N. sativa oil commenced 6 weeks after induction of diabetes at a dose of 400 mg/kg body weight by gastric gavage. Isolated hepatocytes were collected using collagenase to determine liver glucose production. Phagocytic activity was evaluated by injection of fluorescent latex (2 microm diameter) intraperitoneally, followed 24 h later by collection of peritoneal macrophages. N. sativa oil reduced blood glucose from 391+/-3.0 mg/dl before treatment to 325+/-4.7, 246+/-5.9, 208+/-2.5 and 179+/-3.1 mg/dl after the first, second, third and fourth weeks of treatment, respectively. Hepatic glucose production from gluconeogenic precursors (alanine, glycerol and lactate) was significantly lower in treated hamsters. Treatment with N. sativa oil significantly increased the phagocytic activity and phagocytic index of peritoneal macrophages and lymphocyte count in peripheral blood compared with untreated diabetic hamsters. Our data indicate that the hypoglycaemic effect of N. sativa oil is due to, at least in part, a decrease in hepatic gluconeogenesis, and that the immunopotentiating effect of N. sativa oil is mediated through stimulation of macrophage phagocytic activity either directly or via activation of lymphocytes.