p53 Rather Than β-Catenin Mediated the Combined Hypoglycemic Effect of Cinnamomum cassia (L.) and Zingiber officinale Roscoe in the Streptozotocin-Induced Diabetic Model

Abstract

Background: The antioxidant, hypoglycemic, and insulin-enhancing effects of ginger and cinnamon were previously confirmed in experimental and human studies, while the combined effect of ginger and cinnamon was not thoroughly investigated until now. Objectives: This study was designed to assess the antidiabetic effect of combined administration of ginger (Zingiber officinale Roscoe) and cinnamon (Cinnamomum cassia L.) in streptozotocin (STZ)-induced diabetic rats compared to metformin and to explain the mechanism behind this effect. Materials and methods: STZ was utilized to induce diabetes mellitus in male Sprague-Dawley rats. Assessments of fasting blood glucose level (BGL), the total antioxidant capacity (TAC), serum insulin, HOMA-IR, and HOMA-β cells were performed. Pancreatic gene expression of β-catenin and p53 was assessed using RT-PCR. Assessment of histopathological alterations of pancreatic islet cells was performed using routine and immunohistochemical techniques. Results: BGL significantly decreased (p = 0.01), while serum insulin and TAC significantly increased (p < 0.001) in both metformin- and ginger plus cinnamon-treated groups compared to the untreated diabetic group. HOMA-β cell index significantly increased (p = 0.001) in ginger plus cinnamon, indicating their enhancing effect on insulin secretion in diabetic conditions. p53 gene expression was significantly upregulated (p < 0.001), while β-catenin was insignificantly downregulated (p = 0.32) in ginger plus cinnamon-treated groups. Insulin immunoexpression in β cells significantly increased (p = 0.001, p = 0.004) in metformin- and ginger plus cinnamon-treated groups, respectively. Conclusions: The combined administration of ginger and cinnamon has a significant hypoglycemic and antioxidant effect in STZ-induced diabetes mostly through enhancing repair of islet cells mediated via upregulation of pancreatic p53 expression. Therefore, testing this effect in diabetic patients is recommended.

Keywords: antioxidants; cinnamon; diabetes mellitus; ginger; insulin; p53; pancreas; β-catenin.

FIGURE 1

Body weight (A), fasting blood glucose level (B), serum insulin (C), HOMA-IR (D), HOMA–β cells (E), total antioxidants capacity (F), relative expression of β-catenin mRNA (G), and p53 mRNA (H) in the pancreatic tissue of the studied groups are presented. NC: normal control and STZ: streptozotocin. Data are presented as the mean ± SD, n = 6. Comparison between groups was done using one-way ANOVA test followed by LSD post hoc test.

FIGURE 2

Photomicrographs of H&E–stained pancreas of normal control (A) and ginger plus cinnamon–treated control (B) showing normal architecture of the pancreas included the exocrine component and the lightly stained islets of Langerhans. Pancreas of diabetic untreated rat (C) showing some shrunken acini with small dark nuclei and cytoplasm (black arrow). Many islet cells are vacuolated (yellow arrow). Pancreas of diabetic rat treated with metformin (D) or ginger plus cinnamon (E) showing preserved general architecture with most of the acinar and islet cells appear more or less intact apart from few vacuolated cells (H&E × 400). (F): Graph shows the mean area of islets of Langerhans of the studied groups. The area of islets was measured in 10 non-overlapping islets (H&E) per rat. Data are presented as the mean ± SD, n = 6. Comparison between groups was done using one-way ANOVA test followed by LSD post hoc test. Pro Plus image analysis software version 6.0 was used. https://www.mediacy.com/imageproplus.

FIGURE 3

Photomicrographs of pancreas stained immunohistochemically with anti–β-catenin antibody showing mild expression in normal control (A), ginger plus cinnamon (B), diabetic rat treated with metformin (D), and diabetic rat treated with ginger plus cinnamon (E), while that of that diabetic untreated rat (C) showing strong β-catenin expression (anti–β-catenin antibody × 400). (F): graph showing the area percent of β-catenin immunoexpression in the studied groups. NC: normal control and STZ: streptozotocin. Data are presented as the mean ± SD, n = 6. The area percent is measured in at least 20 islets per rat. Compression between groups was done using one-way ANOVA test followed by LSD post hoc test. Pro Plus image analysis software version 6.0 was used. https://www.mediacy.com/imageproplus.

FIGURE 4

Photomicrographs of pancreas stained immunohistochemically with anti-p53 antibody showing few number of p53 +ve cells in the normal control group (A), ginger plus cinnamon–treated group (B), diabetic group treated with metformin (D), and diabetic group treated with ginger plus cinnamon (E), while that of that diabetic untreated rat (C) showing increased number of these cells (anti-p53 antibody × 400). (F): Graph showing the mean number of p53 +ve cells in the studied groups. NC: normal control and STZ: streptozotocin. Data are presented as the mean ± SD, n = 6. The area percent is measured in at least 20 islets per rat. Comparison between groups was done using one-way ANOVA test followed by LSD post hoc test. Pro Plus image analysis software version 6.0 was used. https://www.mediacy.com/imageproplus.

FIGURE 5

Photomicrographs of pancreas stained immunohistochemically with anti-insulin antibody showing moderate expression in almost all β cells of the normal control (A), ginger plus cinnamon (B), and diabetic rat treated with ginger plus cinnamon (E), while that of that diabetic untreated rat (C) showing moderate expression in few β cells and diabetic rat treated with metformin (D) showing moderate expression in many β cells (anti-insulin antibody × 400). (F): graph showing the area percent of insulin immunoexpression in the studied groups. NC: normal control and STZ: streptozotocin. Data are presented as the mean ± SD, n = 6. The area percent is measured in at least 20 islets per rat. Comparison between groups was done using one-way ANOVA test followed by LSD post hoc test. Pro Plus image analysis software version 6.0 was used. https://www.mediacy.com/imageproplus.