Highlighting the novel effects of high-intensity interval training on some histopathological and molecular indices in the heart of type 2 diabetic rats

Abstract

Background: Type 2 diabetes is one of the most common metabolic diseases in recent years and has become an important risk factor for cardiovascular disorders. The first goal is to reduce type 2 diabetes, and in the case of cardiovascular disease, the second goal is to reduce and manage that disorder.

Materials and methods: The rats were divided into 4 groups: Healthy Control (n=8), Diabetes Control (n=8), Diabetes Training (n=8), and Healthy Training (n=8). The protocol consisted of 8 weeks of High-intensity interval (5 sessions per week), where the training started with 80% of the peak speed in the first week, and 10% was added to this speed every week. To measure the level of B-catenin, c-MYC, GSK3B, and Bcl-2 proteins using the western blot method, cardiac pathological changes were measured using hematoxylin and eosin staining, Masson's trichrome and PAS staining and apoptosis using the TUNEL method.

Findings: Histological results showed that diabetes causes significant pathological hypertrophy, fibrosis, and severe apoptosis in heart tissue. HIIT training significantly reduced pathological hypertrophy and fibrosis in heart tissue, and the rate of cardiomyocyte apoptosis was greatly reduced. This research showed that diabetes disorder increases the levels of B-catenin and c-Myc proteins and causes a decrease in the expression of GSK3B and Bcl-2 proteins. After eight weeks of HIIT training, the levels of B-catenin and c-Myc proteins decreased significantly, and the levels of GSK3B and Bcl-2 proteins increased.

Conclusion: This study showed that HIIT could be a suitable strategy to reduce cardiomyopathy in type 2 diabetic rats. However, it is suggested that in future studies, researchers should perform different intensities and exercises to promote exercise goals in type 2 diabetic cardiomyopathy.

Keywords: cardiomyopathy; diabetic; exercise; high-intensity interval training; physical activity.

Figure 1

Schematic view training protocol and heart tissue extraction.

Figure 2

Weight comparison of different groups of rats participating in different stages of the training protocol. *Significant difference between diabetes control and diabetes training groups with healthy control and healthy training groups in the stage before STZ injection; **Significant difference between the diabetes control and diabetes training groups with the healthy control and healthy training groups at the stage of one week after STZ injection; ^#Significant difference between the diabetes control group and other groups in the phase after the end of the exercise; The significance level is p<0.05.

Figure 3

Blood glucose comparison of different groups of rats in different stages of the training protocol. *Significant difference in blood glucose in diabetes control and diabetes training groups with healthy control and healthy training groups at the stage of one week after STZ injection; **Significant difference between diabetes training group and other groups after the end of exercise; The significance level is p<0.05.

Figure 4

The results of Hematoxylin and Eosin (H&E)-stained cardiac tissue. (A) Longitudinal section, (B) cross-section, images represent ×40 magnification and scale bars represent 10 μm. (C) Purkinje cells (fibers) and (D) Collagen area around the arterial vessels, images represent ×10 magnification and scale bars represent 50 μm. (E) Diagram of cardio myocyte cross-sectional area. *Significant difference with all groups (P<0.05). **Significant difference with all groups (P<0.001). ^#Significant difference with diabetic control and healthy control groups (P<0.05). (F) Diagram of Purkinje cells (fibers), *Significant difference with diabetes control and diabetes training groups in Purkinje number cells and significant difference with diabetes control groups in Purkinje cell length and Purkinje cell width (P<0.001). **Significant difference with all groups (P<0.001). ^#Significant difference in diabetes training groups with all groups (P<0.001). Data are expressed as mean ± SEM.

Figure 5

(A) The results of PAS staining of rat heart tissue in diabetic and non-diabetic groups following HIIT exercises to investigate the area of cardiac tissue fibrosis. (B) Diagram of cardiac tissue fibrosis. *Significant difference with diabetes control and diabetes training groups (P<0.001). All images represent ×10 magnification and scale bars represent 50 μm. **Significant difference with all groups (P<0.001). ^#Significant difference with all groups (P<0.05). Data are expressed as mean ± SEM.

Figure 6

(A) The results of Masson’s trichrome staining of rat heart tissue in diabetic and non-diabetic groups following HIIT exercises to investigate the area of cardiac tissue fibrosis. (B) Collagen area around the arterial vessels. All images represent ×10 magnification and scale bars represent 50 μm.

Figure 7

Investigating the apoptosis values of cardiac myocytes of rats in diabetic and non-diabetic groups following HIIT. Green dots show TUNEL positive cells. Fluorescent microscope images represent ×200 magnification.

Figure 8

Evaluation of proteins content using western blot method. (A) The expression of B-catenin, C-myc, GSK3b and Bcl-2 proteins in the heart tissue of rats in different groups. (B–E) The relative ratio of proteins to HPRT levels were determined by image J. *Significant difference in Diabetes Control group with Healthy Control group (P<0.001). **Significant difference in Healthy Training group with all groups in Bcl-2 and GSK3β proteins and significant difference with Diabetes Control and Diabetes Training in B-catenin and C-myc proteins (P<0.05). #Significant difference in Diabetes Training group with all groups in B-catenin, C-myc and Bcl-2 proteins and significant difference with Health Control and Healthy Training in GSK3β protein (P<0.05). Data are expressed as mean ± SEM.

Figure 9

SOD and MDA changes in different groups. *Significant difference in Diabetes Control group with all groups (P<0.001). ^#Significant difference in Healthy Training group with all groups (P<0.001). **Significant difference in Diabetes Training group with Diabetes Control group (P<0.05). Data are expressed as mean ± SEM.