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Sustained cardiac programming by short-term juvenile exercise training in male rats
Y Asif1, M E Wlodek2, M J Black3
1Institute for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Geelong, VIC, 3125, Australia.
The Journal of Physiology
|November 17, 2017
Summary
Juvenile endurance exercise promotes lasting cardiac growth by increasing cardiomyocyte number, leading to sustained heart benefits into adulthood. This cardiac reprogramming effect is most pronounced in young rats and diminishes with age.
Area of Science:
- Cardiovascular Physiology
- Exercise Science
- Developmental Biology
Background:
- Cardiac hypertrophy from endurance training is typically attributed to existing cardiomyocyte enlargement.
- The benefits of endurance exercise on cardiac structure are generally considered transient, regressing after training cessation.
- Juvenile exercise's long-term impact on cardiac development and adult heart health remains incompletely understood.
Purpose of the Study:
- To investigate if juvenile endurance training 'reprograms' the heart for sustained structural and functional improvements into adulthood.
- To compare the effects of exercise training initiated during juvenile, adolescent, and adult life stages.
- To determine the cellular mechanisms underlying exercise-induced cardiac growth in different age groups.
Main Methods:
- Male Wistar Kyoto rats were endurance trained for 4 weeks at juvenile, adolescent, or adult ages.
- Cardiac structure (left ventricle mass, wall thickness, cardiomyocyte number, and cell type proportions) was assessed.
- Gene expression (microRNA-208b) and cardiac function were evaluated at various time points.
Main Results:
- Juvenile exercise induced sustained increases in left ventricle mass, wall thickness, and cardiomyocyte number (+36%) into adulthood.
- Exercise during adolescence had a less pronounced effect, while adult exercise increased cardiac mass without altering cardiomyocyte number.
- Juvenile exercise significantly reduced microRNA-208b expression at 9 weeks, but this effect was not sustained to adulthood.
Conclusions:
- Juvenile endurance exercise induces physiological cardiac hypertrophy with lasting benefits into adulthood, primarily through cardiomyocyte hyperplasia.
- This cardiac reprogramming is most effective during juvenile development and is largely sustained long after training cessation.
- The study reveals a critical window during development for exercise to induce enduring cardiac adaptations.
