Investigation of therapeutic effects of spexin and exercise applications in rats with Type 2 diabetes

Type 2 diabetes mellitus is the most common form of diabetes, which is one of the most common metabolic disorders worldwide. It causes various abnormalities in many systems in the body, especially insulin resistance and oxidative stress caused by hyperglycemia. Although exercise is recommended as part of the management protocol for type 2 diabetes mellitus, the potential effects of spexin on this disease, which has recently been shown to be especially effective on obesity, are also of interest. The aim of this study was to investigate the therapeutic effects of spexin and exercise in male rats with type 2 diabetes. For this purpose, 64 male Sprague-Dawley rats of 6-10 weeks of age with a body weight of 170-200 g were used in the study. The rats were divided into 8 groups, with 10 rats in each diabetic group and 6 rats in each non-diabetic group. Groups; 1st Group: Control Group (phosphate buffered saline), 2nd Group: DM Group (40 mg/kg streptozotocin), 3rd Group: DM+SPX Group (40 mg/kg streptozotocin + 35 µg/kg/day SPX), 4th Group: DM+EGZ Group (40 mg/kg streptozotocin + exercise), 5th Group: SPX Group (35 µg/kg/day spexin), 6th Group: EGZ Group (exercise), 7th Group: SPX+EGZ Group (35 µg/kg/day spexin + exercise), 8th Group: DM+SPX+EGZ Group (40 mg/kg streptozotocin + 35 µg/kg/day spexin + exercise). Type 2 diabetes model was induced by single intraperitoneal administration of 40 mg/kg streptozotocin after 8 weeks of high fat diet. Spexin was dissolved in distilled water and administered intraperitoneally for 21 days. Exercise was also administered by running the rats on a flat treadmill for 21 days in parallel with the administration of spexin. After the 21st day, the rats were sacrificed and serum glucose levels were determined from blood samples. Body weight measurements were also performed at different time points (at the beginning of the experiment, in the 9th week and at the end of the experiment). Malondialdehyde (MDA) and Glutathione (GSH) levels and Glutathione Peroxidase (GSH-Px) and Catalase (CAT) enzyme activities were measured in liver, pancreas and muscle tissues obtained from rats. In addition, FoxO1 and PGC-1α protein expression levels and histopathologic changes were investigated in the same tissues. Based on the findings of the study, the highest initial live weight was measured in the DM+SPX+EGZ group, while the lowest was measured in the control group. The diabetic groups (DM, DM+SPX, DM+EGZ, DM+SPX+EGZ) had higher weights at the beginning compared to the control group and the groups that received only treatment (SPX, EGZ, SPX+EGZ) (p<0.001). In the later stages of the experiment, a significant increase in live weight was observed in the diabetic groups due to the high-fat diet (p<0.001), while decreases were recorded in the treated diabetic groups at the end of the experiment (p<0.001). In terms of serum glucose levels, there was no significant difference between all groups at the beginning of the experiment (p>0.05), while increases were detected in diabetes groups after streptozotocin (p<0.001). Especially in the DM group, glucose levels increased significantly compared to the baseline (p<0.05). At the end of the experiment, decreases in serum glucose levels were observed in DM+SPX, DM+EGZ and DM+SPX+EGZ groups (p<0.001). In DM group, GSH (p<0.001), GSH-Px (p<0.001) and CAT (p<0.05) levels in liver tissue; GSH (p<0.001), GSH-Px (p<0.001) and CAT (p<0.01) levels in pancreatic tissue; and GSH (p<0.001), GSH-Px (p<0.05) and CAT (p<0.05) levels in muscle tissue were found to be low. In addition, MDA levels were found to be increased in DM group, liver (p<0.01), pancreas (p<0.001) and muscle (p<0.001) tissues. Compared to DM group, MDA levels were decreased in liver (p<0.01), pancreas (p<0.001) and muscle (p<0.001) tissues in DM+SPX, DM+EGZ and DM+SPX+EGZ groups. GSH levels were increased in other diabetic groups compared to the DM group only in muscle tissue (p<0.001). In terms of GSH-Px activity, increases were observed only in the pancreas in the DM+SPX and DM+SPX+EGZ groups compared to the DM group (p<0.001), and in terms of CAT activity, increases were observed only in the liver in the DM+SPX+EGZ group compared to the DM group (p<0.05). In this study, the effects of spexin administration and aerobic exercise on FoxO1 and PGC-1α protein expression levels in liver, pancreas and skeletal muscle tissues were investigated in rats with type 2 diabetes model, no significant difference was found between the control group and diabetic groups in terms of FoxO1 protein expression in liver tissue (p>0.05), whereas a significant difference was determined in DM+EGZ and DM+SPX+EGZ groups compared to DM group in pancreas tissue (p<0.01). PGC-1α protein expression was significantly different in the diabetes group in liver and muscle tissues (p<0.001). In addition, a significant difference was detected between DM group and DM+EGZ in liver tissue (p<0.001). In addition, although there was an intergroup difference in PGC-1α expression in pancreatic tissue (p<0.05), no significant difference was found between diabetic groups (p>0.05). Histopathologic examinations revealed that normal histologic structure was preserved in the livers of control, SPX, EGZ and SPX+EGZ groups. Marked hepatocellular macro and microvesicular fatty deposits were observed in the DM group; similar fatty deposits were also observed in the DM+EGZ group (p>0.05). However, the severity of adiposity decreased in the DM+SPX group (p<0.001). In pancreatic histology, normal structure was preserved in the control and non-diabetic experimental groups, and no significant difference was found in islet number and diameters (p>0.05). However, a significant decrease was detected in these parameters in the diabetic groups (p<0.001). Pathologic changes such as karyopyknosis, vacuolar degeneration and capillary congestion were prominent in DM and DM+EGZ groups, while the severity of these findings decreased in DM+SPX and DM+SPX+EGZ groups. No structural changes were observed in the exocrine pancreas in all groups. Masson's trichrome staining revealed that fibrosis increased especially in DM and DM+EGZ groups, whereas fibrotic area decreased in DM+SPX and DM+SPX+EGZ groups (p<0.001). While no lesions were observed in the m. soleus muscle, capillary/muscle fiber ratio increased in DM groups compared to control groups (p<0.001). In conclusion, the effects of spexin and exercise on metabolic, oxidative and histopathological parameters in male rats with type 2 diabetes mellitus were extensively investigated. It was determined that the adverse changes observed in diabetic groups such as hyperglycemia, decrease in oxidative stress markers, adiposity, fibrosis and cellular deterioration in liver and pancreatic tissues were significantly alleviated especially in the group in which spexin and exercise were administered together. It was determined that spexin administration played an important role in lowering glucose levels and supporting the antioxidant defense system, and its use together with exercise strengthened these effects. In line with the data obtained, it was concluded that spexin has therapeutic potential in reducing tissue damage caused by type 2 diabetes and its use in combination with exercise may be promising in the management of diabetes-related complications.