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Modulatory effects of Moringa oleifera extracts on Streptozotocin-induced diabetes in male Wistar rats
Diabetes mellitus (DM) is characterized by deficiency in insulin resulting in hyperglycaemia with metabolic alterations in carbohydrate, lipid and protein. DM has been associated with increased formation of reactive oxygen species (ROS) and inflammatory mediators. Many drugs have been designed for its treatment and management; however, limitations persist in the use of anti-hyperglycemic medications due to numerous side effects, high cost, limited action and secondary failure rates. Moringa oleifera (MO) tree is distributed in the tropics and subtropics and has been found to be very nutritious with a variety of applications. This plant has been reported to possess antidiabetic, antioxidant and other medicinal properties which may be helpful in managing diabetes and its associated complications. This study investigated the antioxidant status, antidiabetic, antilipidemic, anti-inflammatory, anti-apoptotic properties and phytochemical constituents of the leaf extract of MO (250 mg/kg). Diabetes was induced in Wistar rats by a single intraperitoneal injection of streptozotocin (STZ) in buffered citrate (0.1, pH 4.5). Forty-eight Wistar rats were randomly divided into four (4) groups and treated for six weeks: group one- non-diabetic control (Control), group two- non-diabetic Moringa treated (Moringa), group three- diabetic control (Diabetic) and group four- diabetic Moringa treated (Diabetic + Moringa). Methanol, aqueous and petroleum ether extract of MO leaves were evaluated for its antioxidant and phytochemical contents. Assays for total antioxidant capacity such as trolox equivalence antioxidant capacity (TEAC), oxygen radical absorbance capacity (ORAC), ferric reducing antioxidant power (FRAP), flavonoids, flavonols and total polyphenols content were analysed. Other parameters analysed include glucose level; glycated haemoglobin level; hepatic biomarkers; endogenous antioxidants (SOD, CAT, GSH, GPx) in the liver; kidney and erythrocytes; inflammatory biomarkers in the serum, liver and kidney; high-density lipoprotein (HDL), low-density lipoprotein (LDL) and total cholesterol (TC) in serum. Assessment of apoptotic cell death biomarkers (caspase 3, caspase 9, BCL-2, NFKβ, p53) in the liver and kidney were performed. Histopathological analysis was conducted on the liver, kidney and pancreatic sections. In vitro results showed that aqueous and methanol extract of MO demonstrated a high antioxidant capacity, phenolic contents and revealed more chemical constituents than the petroleum ether extract. HPLC analysis of the leaf extract indicated the presence of flavonoids: quercetin, rutin and myricetin and phenolic acids. High levels of polyphenols, flavonols and alkaloids were reported in MO extracts. Treatment with MO in normal and diabetic rats daily for six weeks resulted in significant (p<0.05) decrease in glucose and glycated haemoglobin levels. Liver and kidney size which increased in diabetic rats, decreased significantly (p<0.05) after treatment with MO. Pancreas size showed significant (p<0.05) decrease in diabetic rats and increased significantly (p<0.05) after MO administration. Similarly, serum albumin level increased in non-diabetic and diabetic groups after MO treatment. Also, a significantly increased level of T-bilirubin in diabetic groups relative to normal control rats which reduced greatly after MO administration was observed. Serum lipid profile: LDL and TC levels were increased in rats exposed to STZ. HDL level decreased in diabetic rats when compared to normal control. The activities of MO extracts was shown to lower TC and LDL levels. HDL level also increased after MO administration. Similarly, lipid peroxidation (MDA) level significantly (p<0.05) decreased in the diabetic group following MO treatment. An observable improvement was seen in the antioxidant enzyme system. Activities of antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and concentration of glutathione (GSH) were restored or increased in the homogenate of the liver, kidney, and erythrocytes, indicative of the protective effect of MO in diabetic and non-diabetic rats. The expression of cell death markers (caspase 3, caspase 9, BCL-2, NFKβ, p53) showed remarkable improvement after treatment with MO relative to the non-diabetic control. A significant (p<0.05) reduction in inflammatory cytokines (IL-1α, IL-6, IL-12, IL-18, TNF-α) and (chemokine MCP-1 concentrations) were observed in the serum, liver, and kidney of non-diabetic and diabetic treated groups. Histopathological sections of the liver, kidney and pancreas of diabetic rats revealed severe damage which showed significant improvements after MO treatment. Liver, kidney and pancreatic histological sections revealed the protective effect of MO in both non-diabetic and diabetic rats. MO exerted modulatory effects in STZ-induced diabetes by its antidiabetic, hypoglycemic, antioxidant, anti-inflammatory, anti-apoptotic and anti-lipidemic activities and offered protective effects against diabetic-induced nephrotoxicity and hepatotoxicity, but equally improved antioxidant status. The study concluded that MO could play a significant role in the early treatment and management of diabetes that pharmaceutical industry should consider it in the future as a possible therapeutic agent.