Effect of Aerobic Exercise on Nervous Remolding in Sinus Node and Cardiac Function of Rats with High Fat Diet

A high fat diet can induce fatty infiltration and fibrosis of the cardiac conduction system, which can disrupt the heart's rhythm and lead to cardiac arrest. These changes may involve the remolding of intrinsic cardiac nerve. This study aimed to evaluate the effect of aerobic exercise on the remolding of intrinsic cardiac nerve induced by high fat diet. Methods:Twenty-four male 8-week old Sprague Dawley rats were randomly divided into 3 groups:Control (C) , High fat diet (HF, fat accounted for 45% of kcal) , and High fat diet with Exercise (FE) . FE groups underwent 8-wk of swim training (6 days/week, 1 h/day) . Twenty-four hours after the last training, Color Doppler and ECG were used to evaluate heart function on anesthetized rats. Immunohistochemical technique was used to predict the expression of PGP 9.5, CGRP, and NPY in sinus node zone. Group differences were examined using one-way ANOVA and post-hoc comparisons. Results:1) Compared with the group C, nerve tissue in sinus node zone showed vacuolization and atrophy, and neurons decreased in HF group, which is inhibited or reversed to some extent by aerobic exercise;2) Aerobic exercise changes the distribution of neurotransmitters in the sinoatrial node, with increased CGRP and decreased NPY. 3) Aerobic exercise improved the cardiac function in high fat diet rats, with the increased cardiac ejection fraction, left ventricular shortening fraction, left ventricular systolic internal diameter, left ventricular systolic volume, and thickened myocardial fiber. Conclusions:8-week high fat diet can reduce myocardial contractility and heart pumping function, which maybe involve decreasing intracardiac nerve innervation in sinus node area and imbalanced nervous distribution of CGRP and NPY nerves. Regular moderate-intensity aerobic exercise can reverse these nervous remolding to some extent.