Sport Physiology

Sport Physiology

The Effect of High-Intensity Interval Training and Metformin Administration on some Markers of Myocardial Tissue Injury in Type 2 Diabetic Rats

Document Type : Research Paper

Authors
Tara Maleki 1
khalid Mohamadzadeh salamat 2
kamal azizbeigi 2
1 PhD Student in Exercise Physiology, Department of Physical Education and Sport Sciences, Sa.C., Islamic Azad University, Sanandaj, Iran
2 Associate professor of Exercise Physiology, Department of Physical Education and Sport Sciences, Sa.C., Islamic Azad University, Sanandaj, Iran
10.22089/spj.2026.18775.2415
Abstract
Extended Abstract
Background and Purpose
One of the most serious cardiac complications of diabetes is diabetic cardiomyopathy, which is characterized by structural and functional changes in the myocardium. The loss of cardiomyocytes is a pathological process that triggers an unfavorable myocardial remodeling cascade, which may ultimately lead to heart failure. Damage to cardiac myocytes in diabetic cardiomyopathy leads to the release of specific biomarkers into the bloodstream. The activity of the creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH), as well as troponin I enzymes, are used as key indicators for assessing cell membrane integrity and cardiac cell damage. In addition to protein levels, changes in the expression of genes encoding these proteins, such as the troponin gene, can indicate pathological rearrangement at the molecular level and the cell's attempt to adapt or be a sign of disease progression. The aim of the present study was to investigate the effect of high-intensity interval training (HIIT) and metformin consumption on the expression of the troponin I gene and the activity of creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) enzymes in the myocardium of type 2 diabetic rats.

Materials and Methods
The present study was experimental in design. Thirty 10-week-old male Wistar rats (250-300 grams) were divided into six groups of five: healthy control, diabetic control, placebo, metformin, HIIT, and HIIT+metformin. To induce diabetes, rats were fed a high-fat diet (58% fat, 25% protein, 17% carbohydrate as a percentage of total calories). They were provided with a commercially available rat pellet diet for 2 weeks and then 35 mg/kg streptozocin (STZ, Sigma-Aldrich, USA) dissolved in citrate buffer (0.1 M) pH=4.5 was injected intraperitoneally. Based on previous studies, rats with blood glucose levels above 250 mg/dl 48 hours after injection were considered diabetic. Metformin was obtained from Osvah Pharmaceutical Company (Iran) and was added to the rats' food at a dose of 2.5 g per kilogram of food before pelletizing. Thus, the rats in the metformin and HIIT+metformin groups consumed metformin with their food during the second phase of the intervention. Before the main exercise training began, the rats in the exercise group underwent an adaptation period for one week (5 sessions) on a treadmill, running for 5 minutes at a speed of 6-8 meters per minute with zero incline. The main training protocol lasted for eight weeks, with five sessions per week, starting at 80% of peak speed in the first week and increasing by 10% each week. The speed remained constant in the last two weeks to maintain adaptations. The training sessions consisted of 6x2-minute intervals in the first week, increasing up to 12x2-minute intervals in the seventh and eighth weeks. After each exercise bout, one minute of active recovery at 10 meters per minute was performed. After the intervention, the rats' myocardium was used to measure the expression of the troponin I gene and the activity of the biomarkers CK-MB and LDH. The activity of CK-MB and LDH biomarkers was measured using the spectrophotometric (UV kinetic) method in U/L (activity). Troponin I gene expression was assessed using the RT-PCR method. mRNA levels were normalized to the reference gene GAPDH, and gene expression levels were estimated using the 2^–ΔΔCT formula. After confirming the normal distribution of data using the Shapiro-Wilk test and the homogeneity of variances using Levene's test, one-way analysis of variance (ANOVA) and Tukey's post hoc test were used for statistical analysis. Calculations were performed using SPSS version 30 and GraphPad Prism version 10 software, and the significance level was set at p < 0.05.

Results
Data analysis showed that blood glucose levels were significantly increased in the diabetic control and placebo groups compared to the healthy control group (p<0.001). The metformin, HIIT, and HIIT+metformin groups showed a significant decrease compared to the diabetic control and placebo groups (p<0.001). The HIIT+metformin group had a significant decrease compared to the HIIT group (p=0.003). When comparing the three intervention groups, no significant difference in blood glucose was observed between the metformin, HIIT, and HIIT+metformin groups (p>0.05).The results for troponin I gene expression in cardiac myocytes of diabetic rats also showed a significant increase in the diabetic control and placebo groups compared to the healthy control group (p<0.001). The metformin, HIIT, and HIIT+metformin groups showed a significant decrease compared to the diabetic control and placebo groups (p<0.001). When comparing the three intervention groups, the results showed that the HIIT+metformin group was significantly lower than the metformin group (p<0.001). However, other pairwise group comparisons showed no significant difference (p>0.05).The mean activity of CK-MB in cardiac myocytes of diabetic rats showed a significant increase in the diabetic control and placebo groups compared to the healthy control group (p<0.001). The metformin, HIIT, and HIIT+metformin groups showed a significant decrease compared to the diabetic control and placebo groups (p<0.001). The HIIT+metformin group showed a significant decrease compared to the metformin group (p<0.001). The HIIT group also showed a significant decrease compared to the metformin group (p=0.037). When comparing the three intervention groups, no significant difference in CK-MB was observed between the metformin, HIIT, and HIIT+metformin groups (p>0.05).The mean activity of LDH in cardiac myocytes of diabetic rats showed a significant increase in the diabetic control and placebo groups compared to the healthy control group (p<0.001). The metformin (p=0.010, p=0.004), HIIT (p=0.002, p<0.001), and HIIT+metformin (p<0.001, p<0.001) groups showed a significant decrease compared to the diabetic control and placebo groups, respectively. When comparing the three intervention groups, no significant difference in LDH was observed between the metformin, HIIT, and HIIT+metformin groups (p>0.05).

Conclusion
The present study showed that the induction of diabetes in rats led to a significant increase in cardiac troponin I gene expression and plasma levels of myocardial damage markers, including CK-MB and LDH. These findings indicate the induction of stress and damage in cardiac myocytes due to hyperglycemia. More importantly, the results of the study showed that two different therapeutic interventions, namely high-intensity interval training as a lifestyle modification strategy and metformin administration as a standard drug treatment, were both effective in reducing these indicators and exerting protective effects on the heart. Overall, the findings of this study confirm that the induction of diabetes is associated with damage to cardiac cells. However, the results of the present study show that interval exercise training and metformin medication, both independently and in combination, are able to attenuate these destructive effects and have high potential as therapeutic strategies for protecting the heart in diabetic patients. This synergistic effect not only helps reduce the overall burden of cardiovascular disease in these patients through direct improvement of cardiac indicators but also by optimizing blood glucose control. These results emphasize the importance of a dual approach, including lifestyle modification and optimal drug therapy, for preventing and reducing the burden of cardiovascular disease in the growing population of diabetic patients.

Article Message
This study investigated the effects of High-Intensity Interval Training (HIIT) and Metformin consumption on myocardial tissue damage in rats with type 2 diabetes. Diabetes leads to elevated levels of cardiac cell injury markers, such as CK-MB, LDH, and Troponin I. The results demonstrated that eight weeks of HIIT, Metformin administration, or a combination of both significantly reduced blood glucose levels, myocardial injury biomarkers, and Troponin I gene expression. However, the combination of exercise and medication did not yield a synergistic effect compared to individual interventions. Consequently, both approaches, whether applied alone or combined, are effective strategies for protecting the heart against diabetic complications.

Ethical Considerations
In this study, the principles of animal care were established based on international laws for the protection of laboratory animals and were approved by the Ethics Committee of Islamic Azad University, Sanandaj Branch, with the ID number IR.IAU.SDJ.REC.1404.109.

Authors’ Contributions
Conceptualization: Tara Maleki and Khalid Mohamadzadeh Salamat
Data Collection: Tara Maleki and Khalid Mohamadzadeh Salamat
Data Analysis: Tara Maleki and Khalid Mohamadzadeh Salamat
Manuscript Writing: Tara Maleki and Khalid Mohamadzadeh Salamat
Review and Editing: Khalid Mohamadzadeh Salamat and Kamal Azizbeigi
Responsible for Funding: Tara Maleki
Literature Review: Tara Maleki and Khalid Mohamadzadeh Salamat
Project Manager: Khalid Mohamadzadeh Salamat

Conflict of Interest
No conflicts of interest have been declared by the authors.

Acknowledgments
This research is derived from the doctoral dissertation of Ms. Tara Maleki and has no financial support. We would like to thank and acknowledge all those who contributed to the research.
Keywords
High-intensity interval training
metformin
cardiomyopathy
type 2 diabetes

Subjects

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  • Receive Date 07 November 2025
  • Revise Date 06 January 2026
  • Accept Date 13 February 2026