The Diagnostic and Predictive Potential of miR-328 in Atrial Fibrillation: Insights from a Spontaneously Hypertensive Rat Model

Abstract

Using an atrial fibrillation (AF) model in spontaneously hypertensive rats (SHRs), we aimed to identify circulating miRNAs for AF diagnosis and prediction and to confirm the cardiac origin of these miRNAs. A total of 31 SHRs and 39 Wistar Kyoto (WKY) normotensive controls were randomized into six groups: young, adult, and aging SHR and WKY. Spontaneous AF burden and atrial and circulating levels of 11 miRNAs were quantified. Spontaneous AF was absent in all WKY rats. In the SHRs, AF episodes were observed in two adult animals and in all aging animals (13.6 ± 2.3 episodes/24 h). The atrial levels of five miRNAs were significantly higher in adult and aging SHRs compared to their WKY controls (all p < 0.05). Of these, only the circulating levels of miR-328 were significantly higher in the aging SHRs vs. WKYs (p < 0.0001). Atrial miR-328 levels in the SHRs increased progressively with age (p < 0.001) and correlated with circulating miR-328 levels (r = 0.58; p < 0.01). Among aging SHRs, atrial levels of miR-328 strongly correlated with AF burden (r = 0.79; p < 0.01). These data suggest that the circulating level of miR-328 could emerge as a promising marker for both AF diagnosis and, if assessed dynamically, for AF prediction.

Keywords: animal model; atrial fibrillation; diagnostic biomarkers; microRNAs; predictive biomarkers.

Figure 1

Systolic blood pressure (A) and mean 24 h heart rate (B) in young, adult, and aging normotensive (WKY) rats and spontaneously hypertensive rats (SHRs). # p < 0.01; * p < 0.001; ** p < 0.0001. Data expressed as medians and interquartile ranges; p-values obtained using Mann–Whitney U test.

Figure 2

The left atrial levels of the six microRNAs that had significantly different expressions in the spontaneously hypertensive rats compared to their normotensive controls according to age. The values represent microRNA levels normalized with U6 small nuclear RNA levels. The data are expressed as medians and interquartile ranges; the p-values presented in this figure were calculated using the Mann–Whitney U test; * p < 0.001; ** p < 0.0001.

Figure 3

The circulating levels of the five microRNAs that had significantly different expressions in the spontaneously hypertensive rats compared to their normotensive controls according to age. The values represent microRNA levels normalized with U6 small nuclear RNA levels. The data are expressed as medians and interquartile ranges; the p-values presented in this figure were calculated using the Mann–Whitney U test; * p < 0.01; ** p < 0.001.

Figure 4

Correlations between atrial and circulating levels of the seven microRNAs that were detectable both in the atrium and in peripheral blood in the spontaneously hypertensive rats. The values represent microRNA levels normalized with U6 small nuclear RNA levels. p-values were obtained using the Pearson and Spearman tests, depending on data distribution.

Figure 5

Increased levels of miR-328 in adult and aging SHRs are likely to lead to decreased L-type Ca(2+) current (I_Ca,L) activity and action potential (AP) shortening via the downregulation of CACNA1C and CACNB expression, and, consequently, to the occurrence of premature atrial contractions and atrial fibrillation occurrence. AF—atrial fibrillation; PACs—premature atrial contractions; SHR—spontaneously hypertensive rat; WKY—Wistar Kyoto.

Figure 6

Electrocardiographic tracings showing (A) an atrial fibrillation (AF) episode and (B) premature atrial contractions (PACs).