Melatonin downregulates the increased hepatic alpha-fetoprotein expression and restores pancreatic beta cells in a streptozotocin-induced diabetic rat model: a clinical, biochemical, immunohistochemical, and descriptive histopathological study

Abstract

Background: Diabetes mellitus (DM) is a chronic metabolic disorder. Hepatopathy is one of the serious effects of DM Melatonin (MT) is a potent endogenous antioxidant that can control insulin output. However, little information is available about the potential association between melatonin and hepatic alpha-fetoprotein expression in diabetes.

Objective: This study was conducted to assess the influence of MT on diabetes-related hepatic injuries and to determine how β-cells of the pancreas in diabetic rats respond to MT administration.

Materials and methods: Forty rats were assigned to four groups at random (ten animals per group). Group I served as a normal control group. Group II was induced with DM, and a single dose of freshly prepared streptozotocin (45 mg/kg body weight) was intraperitoneally injected. In Group III, rats received 10 mg/kg/day of intraperitoneal melatonin (IP MT) intraperitoneally over a period of 4 weeks. In Group IV (DM + MT), following the induction of diabetes, rats received MT (the same as in Group III). Fasting blood sugar, glycosylated hemoglobin (HbA1c), and serum insulin levels were assessed at the end of the experimental period. Serum liver function tests were performed. The pancreas and liver were examined histopathologically and immunohistochemically for insulin and alpha-fetoprotein (AFP) antibodies, respectively.

Results: MT was found to significantly modulate the raised blood glucose, HbA1c, and insulin levels induced by diabetes, as well as the decreased alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Furthermore, MT attenuated diabetic degenerative changes in the pancreas and the hepatic histological structure, increased the β-cell percentage area, and decreased AFP expression in the liver tissue. It attenuated diabetes-induced hepatic injury by restoring pancreatic β-cells; its antioxidant effect also reduced hepatocyte injury.

Conclusion: Collectively, the present study confirmed the potential benefits of MT in downregulating the increased hepatic alpha-fetoprotein expression and in restoring pancreatic β-cells in a streptozotocin-induced diabetic rat model, suggesting its promising role in the treatment of diabetes.

Keywords: STZ; alpha-fetoprotein expression; diabetes; histopathology; liver; melatonin.

Figure 1

Photomicrograph of rat pancreas sections stained with H&E stain from the control negative (A, B) and MT control groups (C, D) demonstrating the following: normal pancreatic structure and architecture in the form of (A, C) normal-sized islets of Langerhans showing the normal density of islet cells (IL) and normal exocrine acinar cell (thick arrows). (B, D) Normal intralobular duct (arrowheads) and normal blood vessels (thin arrows).

Figure 2

Photomicrographs of pancreas sections stained with H&E stain (A–D) from the DM group showing the following: (A) Islets of Langerhans, which undergo depletion and necrobiotic changes in their constituent cells (Circle), and necrotic acinar cells (arrowheads). (B) Islets of Langerhans showing vacuolated degeneration in most cells (arrows), capillary hemorrhage inside islets green arrowhead), and the intralobular duct dilated with secretion (Star). (C) Dilated and congested blood vessels with a thick vascular wall (arrow). (D) Thickening of the wall of the blood vessel (thin arrows), the exocrine acinar cells showing degeneration and dissociation (red arrows).

Figure 3

Photomicrograph of pancreas sections stained with H&E stain from the DM+MT treated group showing the following: (A) Well-defined islets of Langerhans with proliferated cell population (arrow, ILS) in between normal pyramidal acidophilic pancreatic acini (white arrowheads). (B) Normal vascular structure (arrowhead) and normal intralobular duct (arrows).

Figure 4

Histomorphometry graph showing semiquantitative measurements of pancreatic tissue sections among the experimental groups: (A) Islets of Langerhans atrophy, (B) Vacuolar degeneration in the islets of Langerhans, and (C) Vascular congestion. Data are expressed as means ± standard deviations. Significant differences vs. the control group are marked by different asterisks through one-way ANOVA with Tukey's post-hoc test: *P ≤ 0.05, ***P ≤ 0.001.

Figure 5

Photomicrographs of hepatic tissue sections stained with H&E stain from the control negative (A, B) and MT control groups (C, D), showing the following: normal histological hepatic architectures compromising in (A, C). Normal central veins (stars), normal hepatocytes arrangement, and a structure with normal vesicular nucleus (arrows). (B, D) Normal portal triad structure present in the normal portal vein (arrows), hepatic artery (red arrow), and bile duct (arrowheads).

Figure 6

Photomicrographs of liver sections stained with H&E stain from the DM untreated group showing the following: (A, B) Congested central veins (C.V). (C) Congestion and dilatation in hepatic sinusoids (arrows). (D) Hepatocellular degeneration (arrows) and mononuclear inflammatory cellular infiltration (arrowhead). (E) Focal mononuclear cellular aggregation (arrowheads). (F) Fibrous tract (FT) connecting between portal areas and surrounding the congested portal veins (PV). (G) Inflammatory cellular infiltration in the fibrous tract (arrowheads). (H, I) Portal areas showing the following: Severe dilatation and congestion in portal veins (PV) and periportal fibrosis infiltrated with inflammatory cells (arrows).

Figure 7

Photomicrographs of liver sections stained with H&E stain from DM+MT treated rats showing the following: (A, B) Normal central vein (CV), normal hepatocellular architecture (H), and mild interstitial hemorrhage (arrows). (C) Normal central vein (star) and mild mononuclear cellular aggregation (arrowheads). (D) Portal area; mild congested portal vein (star) surrounded with mild fibrosis (arrows).

Figure 8

Histomorphometry graphs showing semiquantitative measurements of hepatic tissue sections among the experimental groups: (A) Hepatocellular alterations (B) vascular congestion (C) fibrosis. Data are expressed as means ± standard deviations. Significant differences vs the control group are marked by different asterisks through one-way ANOVA with Tukey's post-hoc test: *P ≤ 0.05, ***P ≤ 0.001.

Figure 9

Photomicrographs of pancreatic sections of (A) Control and (C) MT group, both showing the expression of insulin in islet β-cells. (B) DM group showing decreased islet β-cells (D) DM+MT group showing increased islet β-cells. (E) Histogram representing the mean percentage area of insulin expression in all groups. Significant differences vs. the control group are marked by different asterisks through one-way ANOVA with Tukey's post-hoc test. ***P ≤ 0.001); ns, non-significant vs. control.

Figure 10

Photomicrographs of liver sections of (A) Control and (C) MT group, both showing minimal expression of AFP in hepatocytes (B) DM group. Showing the expression of AFP in most hepatocytes (D) DM+MT group showing the expression of AFP in few hepatocytes compared with the diabetic group. (E) Histogram representing the mean percentage area of AFP expression in all groups. Significant differences vs. the control group are marked by different asterisks through one-way ANOVA with Tukey's post-hoc test. ***P ≤ 0.001); ns, non-significant vs. control.