PURPOSE: 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 a 10-wk high fat diet.
METHODS: Thirty-two male 8-week old Sprague Dawley rats were randomly divided into 4 groups: Control (C), High fat diet (H, fat accounted for 45% of kcal), Exercise (E), and High fat diet with Exercise (HE). E and HE groups underwent 10-wks 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 and heart rate variability on anesthetized all 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: The impact of high fat diet and exercise and their interaction on the key outcome variables is summarized as follows: For Ejection Fraction (%), Group H (27.6±3.2) was the lowest, followed by Groups HE (32.2±5.1), C (41.4±6.5) and E (58.2±3.9) (selected effect size [SES]: H vs. C = 2.7, p<0.01; HE vs. H = 1.1, p<0.05; & E vs. C = 3.1, p<0.01); For High Frequency Power (ms2), Group H (0.33±0.06) was the smallest, followed by Groups HE (0.36±0.03), C (0.44±0.01) and E (0.45±0.03) (SES: H vs. C = 2.6, p<0.01; HE vs. H = 0.6, p>0.05, & E vs. C = 0.6, p>0.05); For the quantity of PGP 9.5 positive cells, Group H (2874±42) had the fewest, followed by Groups HE (3037±35), C (3396±27) and E (3677±12) (SES: H vs. C = 14.8, p<0.01; HE vs. H = 4.0, p<0.05; & E vs. C = 13.5, p<0.01); For CGRP/NPY, Group H (0.28±0.05) has the minimum ratio, followed by Groups HE (0.68±0.1), C (0.74±0.2 and E (1.19±0.4) (SES: H vs. C = 3.2, p<0.01; HE vs. H = 5.1, p<0.01; & E vs. C = 1.4, p<0.01).
CONCLUSIONS: A 10-wk high fat diet can reduce myocardial contractility and heart pumping function, which maybe involve decreasing autonomic nervous 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.