The Effect of Eight Weeks of Interval Training and the Use of Atorvastatin on the Expression of the Hepatic VEGF-Β Gene in Male Wistar Rats Model of Type 1 Diabetes

Background &

Diabetes is a chronic non-communicable disease characterized by chronic hyperglycemia caused by a defect in the secretion and function of the pancreatic insulin hormone. This disease is a group of metabolic diseases and is considered as a progressive global health problem (1, 2). In general, diabetes is divided into type 1 diabetes, type 2 diabetes and gestational diabetes based on the cause and clinical features (3-5). Type 1 diabetes was recently termed juvenile-onset diabetes or insulin-dependent diabetes mellitus, a condition caused by destruction of pancreatic β-cells by T cells resulting in complete insulin deficiency (2 , 5). Type 1 diabetes represents 5 to 10% of patients with diabetes (2). Type 1 diabetes is characterized by the destruction of more than 90% of β cells. Streptozocin (STZ) is a standard method for inducing diabetes in animals (6). Vascular endothelial growth factor beta (VEGF-β) is one of the obscure members of the VEGF family. It has been reported that the ability of VEGF-β to induce angiogenesis is weak in most tissues. However, VEGF-β appears to be a more tissue-specific vascular growth factor that can have nutritional and metabolic effects (8). In early 2008, Karpanen et al stated that VEGF-β has a weak role in the vascular system; But it has a significant advantage in regulating lipid metabolism (9). Considering the potential of VEGF-β in regulating lipid metabolism, it is expected that this growth factor will become a new target for improving metabolic diseases, such as obesity and diabetes (10). Defects in multiple VEGF-β pathways have been reported to be associated with increased cell apoptosis in diabetes models (11). However, the potential beneficial effects of VEGF-β through increasing blood flow (increasing insulin availability and glucose uptake in target organs) and decreasing FAs uptake (preventing lipotoxicity and improving insulin signaling) and its safety for clinical use , has not yet been determined (21). which indicates the need for more research in this regard. Previous research indicates the positive effects of exercise on blood sugar control and also reducing the complications caused by diabetes (5, 13, 14). Also, one of the main and most effective drugs that have beneficial effects on lipid profile are statins; Among statins, atorvastatin is considered one of the least complicated and most effective. This drug is a selective competitive inhibitor of the enzyme 3-hydroxy-3-methylglutaryl coenzyme-A reductase, but unlike other statins, it is a completely synthetic compound that is used in diabetic patients with hypercholesterolemia in combination with other sugar control drugs. The beneficial effect of atorvastatin on some adipokines has been proven and it seems to be one of the mechanisms of the effect of this drug in blood sugar control (15). According to the mentioned information, the present research was conducted with the aim of comparing the effect of eight weeks of interval training and atorvastatin consumption on hepatic VEGF-β gene expression in male Wistar rats’ model of type 1 diabetes.

In this study, 25 mice were divided into Healthy control, diabetes control, diabetes + interval training, diabetes +atorvastatin, and diabetes + atorvastatin+ interval training groups.The interventions included eight weeks of interval training, running on a treadmill and taking 10 mg of atorvastatinby gavage.After the interventions, the mice were sacrificed and the liver tissue was analyzed.Statistical analysis was performed using one-way analysis of variance and Tokey post hoc test.

The results showed that the induction of diabetes caused a significant decrease in hepatic VEGF-β compared to the healthy control group. In the groups of diabetes + interval training, diabetes + atorvastatin and diabetes + atorvastatin + interval training, the increase of VEGF-β was significant compared to diabetes control group (P < 0.001), but no difference was observed between the three intervention groups (P < 0.05).

The results of our research showed that after induction of diabetes, the expression of hepatic VEGF-β gene in diabetic groups was significantly lower than in the healthy control group. The results of Shahavand et al also showed that the induction of diabetes decreased the expression of VEGF-β gene in the heart tissue of diabetic rats (18), which was consistent with the results of the present study. VEGF-β has been reported to be involved in lipid and glucose metabolism (10). Also, in mice in which VEGF-β was knocked out and fed with high fat, in addition to obesity and dyslipidemia, their liver suffered from steatosis and increased insulin resistance (19). Research has shown that VEGF-β can reduce lipid accumulation and restore insulin sensitivity in NAFLD (10); Therefore, the decrease of VEGF-β caused by diabetes is related to the liver complications of diabetes such as hepatic steatosis and hepatic insulin resistance. It can be said that by inducing diabetes and increasing hyperglycemia caused by diabetes, the level of VEGF-β decreases; which can be related to liver complications caused by diabetes such as non-alcoholic fatty liver and apoptosis of hepatocytes. However, Ye et al.'s study reported that plasma VEGF-β levels were significantly higher in subjects with NAFLD compared to subjects without NAFLD, and analysis of covariance confirmed this result (20). The reason for the difference in the results may be due to the difference in the research samples, the difference in the studied tissue, research units or the type of disease. Because in our research, the research samples included diabetic rats treated with streptozotocin, which were different from the research samples of Ye et al. In examining the effect of aerobic exercise on hepatic VEGF-β gene expression, the results of the present study showed that intermittent exercise increased VEGF-β gene expression compared to the control diabetes group. Shahavand et al also reported that six weeks of continuous aerobic exercise increased cardiac VEGF-β gene expression in diabetic rats (18), which is consistent with the results of the present study. Kivelä et al also reported in their research that an exercise training increased the expression of VEGF-β in healthy mice (21). VEGF-β and mitochondrial gene expression are regulated in concert, and endogenous VEGF-β levels are highest in tissues with high metabolic activity, such as heart, skeletal muscle, and brown fat (25). It has been reported that the lack of VEGF-β leads to a decrease in the expression of fatty acid (FA) transfer proteins (Fatp3 and Fatp4) in endothelial cells, which is associated with a decrease in lipid droplets in the heart and skeletal muscle fibers (26) and improved sensitivity to Insulin has been implicated in diabetic models (27). Considering that the liver is also a metabolically active tissue, and on the other hand, it has been reported that regular exercise can increase the body's overall metabolism and, as a result, the liver's activity to finance long-term activities (28); Therefore, the increase of VEGF-β can be attributed to the improvement of mitochondrial activity in the liver in adaptation to regular exercise. Other results of the current research also showed that the use of atorvastatin increased the expression of the hepatic VEGF-β gene compared to the control diabetes group. Atorvastatin, an HMG-CoA reductase inhibitor, is widely used in the treatment of dyslipidemia (29). In a human study, atorvastatin 10 mg daily has been reported to be safe and effective in reducing the risk of first cardiovascular events, including stroke, in patients with type 2 diabetes without elevated LDL cholesterol (31). It can be said that part of these anti-diabetic effects of atorvastatin is related to the effects of this drug on improving fat metabolism in the liver.In the investigation of the interactive effect of interval training and atorvastatin consumption, the results of this research showed that in the interactive group, although a significant increase in the expression of the hepatic VEGF-β gene was observed compared to the control diabetes group, these changes were not compared to the diabetes + exercise and diabetes + groups. Atorvastatin was not significant; it seems that the combined use of exercise and atorvastatin does not have a greater advantage on hepatic VEGF-β gene expression than either method alone.