Minimization of the risk of diabetic microangiopathy in rats by Nigella sativa

Background: Microangiopathy is a chronic diabetic complication resulting from metabolic derangements, oxidative stress, and increased pro-inflammatory cytokine production. Nigella sativa Linn. is used as an herbal medicine that exerts hypoglycemic, antilipidemic, anti-inflammatory, and antioxidant effects. Objective: To examine the effects of N. sativa extract on cutaneous microvascular changes in diabetic rats. Materials and Methods: Sprague-Dawley rats were randomly assigned into the following four groups: Untreated and N. sativa-treated normal controls and untreated and N. sativa-treated rats with streptozotocin-induced diabetes. A cold-pressed N. sativa extract was then orally administered (1000 mg/kg/day). After 8 weeks of treatment, the glucose, glycosylated hemoglobin (HbA_1c), tumor necrosis factor-alpha (TNF-α), insulin levels, and lipid profile were determined in cardiac blood. Dermal capillary wall thickness was measured in tail skin sections stained with periodic acid-Schiff. Endothelial apoptosis was morphologically evaluated by hematoxylin and eosin staining. Results: Diabetes significantly reduced the circulating insulin and low-density lipoprotein levels and caused elevations in the glucose, HbA_1c, and triglyceride levels, accompanied by a slight increase in total cholesterol levels and no change in the high-density lipoprotein and TNF-α levels. Capillary basement membrane thickening and a decreased capillary luminal diameter despite no evidence of endothelial cell apoptosis were also observed. N. sativa treatment of diabetic rats reduced the mean HbA_1cconcentration by 1.4%, enlarged the capillary lumens, and tended to attenuate dermal capillary basement membrane thickening without affecting the lipid profile or TNF-α level. Conclusion: Our results indicate that N. sativa may be used to minimize the risk of diabetic microangiopathy, potentially due in part to its glycemic control activity.