A Custom Analysis of RR Interval Properties Reveals Alterations of the Brain-Heart Axis in Experimental Animals with Metabolic Syndrome
Résumé
Background Metabolic Syndrome (MetS) is a cluster of conditions that increases the risk for cardiovascular complications and all-cause mortality. MetS manifests with reduced heart rate variability (HRV), but factors underlying the process remain to be fully elucidated. Objectives To gain new insights into the effects of MetS on heart rhythm dynamics, we developed a custom algorithm to analyze the distribution and span of the RR intervals. Methods MetS was induced in male and female mice by Western diet feeding (WD mice), whereas animals on regular chow were used as control (Ctrl mice). The sequence of RR intervals of ECGs and their deviation were sorted and normalized using an approximation of the distribution function to obtain sequences of RR interval duration (sortRR) and RR interval deviation (sortRRdev). Results SortRR sequences revealed shorter intervals in WD mice compared to Ctrl within the range of intermediate and long RR intervals, indicating that mice with MetS have limited capability to lower heart rate. Moreover, sortRRdev sequences had smaller amplitudes for WD mice, consistent with reduced HRV. Inhibition of sympathetic inputs abrogated differences of sortRR sequences for the two groups of mice, whereas inhibition of parasympathetic inputs suppressed differences in the sortRRdev series. Interestingly, Western diet feeding in animals lacking β-adrenergic receptors minimally affected heart rate dynamics in female mice, but revealed significant alterations in male animals, which were abrogated by parasympathetic inhibition. Conclusion These results support the notion that sympathoexcitation and parasympathetic withdrawal occur with MetS by affecting duration, functional range, and variability of RR interval.
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