Effects of supraphysiological doses of testosterone and exercise training on insulin like growth factor I concentration in left ventricles

Abstract

Introduction: Anabolic-androgenic steroids are increasingly used in athletes and non-athletes elderly males. Several studies have suggested that synthetic testosterone have direct effects by causing cardiac hypertrophy and left ventricular contractile dysfunction. All of these factors contribute to an increased risk of ventricular arrhythmias and sudden cardiac death. However, limited data are available regarding interactions between anabolic hormones concentration and insulin-like growth factor I (IGF-I) expression in the heart in response to exercise training. Therefore, we examined effects of supraphysiological testosterone administration on left ventricular remodeling and cardiac IGF-I concentrations in sedentary and exercise-trained rats. Methods: Male Wistar rats (n=52) were randomly allocated to groups with a 6-week endurance training with or without testosterone, and sedentary animals with or without testosterone. The hormone (20mg/250 g BW) was administrated once a week for six weeks. After six weeks the animals were anesthetized and the heart was excised and weighted. The left ventricular was separated to biochemical analyses. Results: Testosterone treated sedentary animals showed significant higher cardiac IGF-I concentrations compared to control group (p<0.001). In endurance-trained groups, cardiac IGF-I concentrations were significantly higher after testosterone administration (p<0.01). The administration of supraphysiological testosterone significantly increased left ventricular mass of sedentary rats and left ventricular mass to body weigh ratio in endurance trained animals compared to control group. However, this effect was relatively small in trained group with and without testosterone administration. Conclusions: The data demonstrate that increased cardiac IGF-I concentration in response to higher serum testosterone might be responsible for heart hypertrophy observed in both sedentary and endurance- trained animals.