The effects of moderate physical exercise on cardiac hypertrophy in interleukin 6 deficient mice

Prolonged physical training leads to compensatory changes in cardiovascular system. One of the most important of them is cardiac hypertrophy. The knowledge, which factors contribute to cardiomyocyte hypertrophy caused by physical exercise is still incomplete. Interleukin 6 (IL6) secreted by contracting skeletal muscles may affect cardiac hypertrophy and remodeling. The aim of the study was to investigate the role of IL6 in exercise induced cardiac hypertrophy.

Female mice lacking functional IL6 gene C57BL6/J(IL6-/-tm1Kopf) (IL6KO) and age and sex matched controls C57BL6/J (WT) were subjected to 6 week swimming regime. Twenty-four hours after the last training session the mice were sacrificed, hearts were excised and weighed. Two other groups of sex and strain matched mice (9 in each group) not subjected to physical training, were sacrificed and served as controls. Weights of the heart and the left ventricle were related independently to the body weight and the tibia length as measures of hypertrophy. Statistical analysis was performed using multifactorial ANOVA and the Fisher test.

There was significantly higher heart/body weight ratio in both groups of mice which were trained as compared to the respective sedentary animals [F(3,30) = 31.085 p < 0.001] There were, however, no significant differences between respective WT and IL6KO groups. Similar relations were found for the left ventricle and also when the weights of the heart and the LV were related to the tibia length.

IL6 is not necessary for cardiac hypertrophy induced by prolonged moderate physical exercise in mice. Additional study is warranted to elucidate this phenomenon.