Improving endothelial function following regular pyramid aerobic training in patients with type 2 diabetes

In recent years, increasing attention has been paid to the role of endothelium in the development of cardiovascular disease. Endothelial dysfunction is now considered a major step in atherosclerosis (3). Vascular endothelial cells play a key role in maintaining cardiovascular homeostasis in health (7). Unlike other tissues and cells that are not affected by abnormal systemic glucose concentrations, vascular endothelium is highly sensitive to changes in blood sugar. Thus, vascular endothelium is probably the main target of hyperglycemic injury (5). Endothelial dysfunction and atherosclerosis are associated by several mechanisms (8). Flow-dependent vasodilation (FMD) refers to the dilation of an artery when blood flow increases in that artery (8). Endothelial function as a predictor of cardiovascular events is measured by measuring FMD in the brachial artery and is independently associated with adverse cardiac outcomes (8, 9). Exercise is a useful and inexpensive way to prevent and treat metabolic disorders such as type 2 diabetes, and according to previous studies, active lifestyle and exercise training can control glycemic and also reduce cardiovascular complications in these patient (1, 10). One of the most common methods in the training program for patients with type 2 diabetes is aerobic exercise; Due to its low cost and the possibility of performing these exercises in different places, it can be a widely used training method (11, 12). An activity in which a person is able to perform this activity for a long time and the dominant energy system in these activities is through the oxidative or aerobic system is called aerobic activity (13); In aerobic exercise, the intensity of exercise can be increased (14); It is also possible to adjust the running time or running distance in proportion to the increase in intensity of the training in a pyramid, to increase the ability to perform. Considering endothelial dysfunction in type 2 diabetes (4) and considering that endothelial dysfunction is a precursor to atherosclerosis (3), the use of effective treatment methods to improve endothelial function is of particular importance. Although much research has been done on the effect of aerobic exercise on endothelial function health, which is mainly evaluated by FMD (15), However, only a few studies have evaluated the effect of aerobic exercise specifically on endothelial function in type 2 diabetic patients (5, 16), which indicates the need for further research in this field. Since no specific study has been performed to investigate the effect of pyramidal aerobic exercise on vascular function in type 2 diabetes, the aim of the present study was to determine the effect of eight weeks of pyramid aerobic training on flow-dependent vasodilation in patients with type 2 diabetes.

In the present quasi-experimental study, 60 patients with type 2 diabetes were selected by randomly sampling method and divided into two training and control groups. Anthropometric characteristics as well as resting blood pressure, FMD and VO2max of the subjects were measured before the start of the study. 48 hours after the intervention period, the research variables were measured again. Exercise intervention in the present study consisted of eight weeks, 3 sessions per week and each training session included 45-60 minutes of pyramid aerobic training that was performed in three pyramidal intervals. The volume of each training interval, based on the intensity of training and the ability of the subjects, started from light intensity in the first interval and increased in each interval. The intensity of exercise was calculated according to the reserve heart rate of each individual and using the kavonen formula (11). Paired Samples t Test and Analysis of covariance (ANCOVA) were used for statistical analysis. SPSS software version 26 and significance level (P ≤ 0.05) were used for statistical analysis.

After eight weeks of training, there were funded a significant decrease in systolic and diastolic blood pressure and a significant increase in FMD and VO2max compared to the pretest and control groups (P < 0.001).

The results showed that eight weeks of pyramidal aerobic exercise significantly reduced systolic and diastolic blood pressure and also significantly increased VO2max and FMD in the exercise group compared to the control group. Maiorana et al. (16), Chasland et al. (18), and Bailey et al. (19) also reported in their research that exercise increases FMD, which is consistent with the results of the present study. Vascular endothelial function is essential for maintaining healthy vessel wall and vasomotor control. These functions are due to the production of numerous autacoids, especially nitric oxide (NO) (20). Due to the fact that blood pressure is affected by the diameter of blood vessels, the reduction in systolic and diastolic blood pressure in the present study can be attributed to the improvement of vascular dilation. Mendes et al. also reported a significant reduction in systolic and diastolic blood pressure in patients with type 2 diabetes after a 9-month exercise program (24), which was consistent with the results of the present study. The results of Han et al.'s study showed that high blood pressure is associated with endothelial dysfunction and is among the potential risk factors for baseline FMD, (including old age, male gender, high systolic blood pressure, or higher hs-CRP levels) May increase blood pressure by decreasing FMD (17). According to the results of the present study, it can be said that one of the effective factors in reducing blood pressure in patients with type 2 diabetes is vascular adaptation after exercise and thus improving endothelial function. Also, along with the increase in FMD, a significant increase was observed in the VO2max of the subjects, which was in line with the results of the research of Wona et al. (25) and Cornelissen et al. (26). Higher dilatation levels due to flow indicate better vascular adaptation to aerobic exercise (28). Therefore, it can be said that the improvement of VO2max in the present study is the result of vascular adaptation and consequently increased blood flow due to improved endothelial function. According to the results, it can be suggested that this training system be used to improve athletic performance as well as reduce cardiovascular risk factors in patients with type 2 diabetes. Therefore, it can be said that the improvement of VO2max in the present study is the result of vascular adaptation and consequently increased blood flow due to improved endothelial function. According to the results, it can be suggested that the pyramidal aerobic training system be used to improve athletic performance as well as reduce cardiovascular risk factors in patients with type 2 diabetes.