The intensive physical activity is often associated with cardiac changes, particularly involving the right ventricular (RV) chamber. However, the molecular mechanisms involved in the RV physiologic adaptation to long-term training are not completely understood. In the present study we investigated the role of the growth hormone/insulin like growth factor 1 (GH/IGF-1) axis in the RV remodeling of athletes.
Nineteen male top levels rowers and 19 age-matched healthy sedentary male controls underwent blood determination of fasting serum GH, IGF-1, IGF binding protein 3 (IGFBP-3) and acid-labile subunit levels and standard Doppler echocardiography combined with pulsed Tissue Doppler of RV tricuspid annulus. Myocardial pre-systolic (PSm), systolic (Sm), early diastolic (Em) and atrial (Am) velocities as well as myocardial time intervals adjusted for heart rate were calculated.
Rowers had serum IGF-1 levels (P<0.05), RV internal chamber size (P<0.05) and RV wall thickness (P<0.0001) significantly higher than controls. Additionally, rowers had improved RV systolic (higher tricuspid annular systolic excursion, higher PSm and Sm velocities; lower myocardial pre-contraction time) and diastolic function (lower A velocity, shorter deceleration time, isovolumic relaxation time and myocardial relaxation time; higher E/A ratio, Em and Em/Am ratio) compared to controls. In the rowers, IGF-1 was associated with PSm velocity (r=0.55, P=0.01) and myocardial pre-contraction time (r=−0.57, P=0.01), GH with pre-ejection period (r=−0.50, P<0.05) and Em (r=0.47, P<0.05). These associations remained significant after adjusting for age, heart rate and body surface area.
In conclusion, this study shows for the first time that the GH/IGF-1 axis is responsible for the RV functional remodeling in high-top rowers, improving mainly the systolic activity. This effect seems to be primarily modulated by the IGF-1 overproduction, as a physiological adaptation to prolonged training.