Black Seed Thymoquinone Improved Insulin Secretion, Hepatic Glycogen Storage, and Oxidative Stress in Streptozotocin-Induced Diabetic Male Wistar Rats

Abstract

Diabetes mellitus is one of the metabolic diseases having several complications. Nigella sativa oil (NSO) might have beneficial effects in the treatment of diabetic complications. Thirty-two mature male Wistar rats were equally divided into four experimental groups: control, control NSO 2 mL/kg, streptozotocin- (STZ-) induced diabetic, and diabetic (STZ-induced) treated with oral NSO 2 mg/kg for 30 days. Fasting blood glucose (FBG), insulin, and lipid profile levels were determined. Pancreatic and hepatic tissues were used for catalase and GSH. Histopathology, hepatic glycogen contents, insulin immunohistochemistry, and pancreatic islet morphometry were performed. NSO 2 mL/kg was noticed to decrease (P < 0.05) FBG and increase (P < 0.05) insulin levels in diabetic rats than in diabetic nontreated animals. Lipid profile showed significant (P < 0.5) improvement in diabetic rats that received NSO 2 mL/kg than in the diabetic group. Both pancreatic and hepatic catalase and GSH activities revealed a significant (P < 0.05) increment in the diabetic group treated with NSO than in the diabetic animals. NSO improved the histopathological picture and hepatic glycogen contents of the diabetic group as well as increased (P < 0.05) insulin immunoreactive parts % and mean pancreatic islet diameter. NSO exerts ameliorative and therapeutic effects on the STZ-induced diabetic male Wistar rats.

Figure 1

Nigella seed oil extract effect on pancreatic histopathology in normal and STZ-induced diabetic rats. (a and b) Control- and NSO- (2 mL/kg) treated control groups: normal control rat displayed healthy islets of Langerhans. (c) Diabetic control: arrow displays the atrophied islets of Langerhans. (d) NSO- (2 mL/kg) treated diabetic rats display bigger islets of Langerhans than do diabetic untreated group (arrowhead). Scale bar represents 50 μm.

Figure 2

H&E stain of liver: (a) control group and (b) Nigella-treated rats demonstrate normal hepatic architecture showing the classic lobule with the central vein at the center and portal tracts at the periphery; each one is separated from the others by a similar distance, 100x. (c) Diabetic group showing ballooning degeneration of the hepatocyte (^∗, 40x), and interface hepatitis (arrow), 100x. (d) NSO-treated diabetic group showing restoration of normal architecture, 100x. Scale bar represents 100 μm.

Figure 3

PAS stain of liver: (a) control group and (b) NSO- (2 mL/kg) treated control rats demonstrate abundant glycogen, which is present within the cytoplasm of the hepatocytes (magenta-colour granules), 400x. (c) Diabetic group demonstrates marked reduction in PAS positivity (few scattered glycogen granules), 400x. (d) NSO- (2 mL/kg) treated diabetic group demonstrates restoration of PAS positivity, 400x. Scale bar represents 50 μm.

Figure 4

Immunohistochemical staining for insulin expression in pancreatic islets from different experimental groups. (a) Control, (b) NSO- (2 mL/kg) treated group, (c) diabetic group, and (d) diabetic group treated with NSO (2 mL/kg). Scale bar represents 50 μm.