Susceptibility of female rats to cardiac arrhythmias following refeeding after severe food restriction

Fig. 1. Effect of 3 months refeeding after severe food restriction on body weight gain and food intake. Change in A body weight (BW) and B food and C water intake compared to baseline in female (F, purple circle, red square; n = 9/group) and male (M, black circle, green square; n = 8/group) rats maintained on a normal diet for the duration of the study (CT, circle) or for 3 months after a 2-week severe food restricted period (sFR-Refed, square). Values are expressed as the mean ± SEM; #p < 0.05 vs. CT, same timepoint, same sex and *p < 0.05 vs. F, same diet, same timepoint by two-way ANOVA and Bonferroni post-hoc test

Fig. 2. Effect of 3 months refeeding after severe food restriction on cardiac pathology in the isolated heart. A–H Representative sections of the left ventricle of the heart after staining with hematoxylin and eosin (H&E) in female (F) and male (M) rats maintained on a normal diet for the duration of the study (CT) or for 3 months after a 2-week severe food restricted period (sFR-Refed) at 200× (A–D) and 1000× (E, F) magnification. Images are representative of five rats per group. Grater interstitial space (blue arrow) is observed in F—compared to M-sFRRefed rats, while fiber constrictions (black box) and focal cell lysis (black circle) are more prevalent in M-sFR-Refed rats. I Gaussian Kernel density estimates of cardiomyocyte thickness from H&Estained hearts. The color coded vertical dashed lines represent the mean in each animal group. J The percentage of cardiomyocytes below (A, atrophied) and above (H, hypertrophied) the cardiomyocyte diameter normal (N) range (depicted by two black vertical lines). Values are expressed as the mean ± SEM; #p < 0.05 vs. CT, same sex and *p < 0.05 vs. F, same diet by two-way ANOVA and Bonferroni post-hoc test

Fig. 3. Effect of 3 months refeeding after severe food restriction on collagen deposition in the isolated heart. A–D Representative sections of the left ventricle of the heart after staining with Masson’s trichrome in female (A and C) and male (B and D) rats maintained on a normal diet for the duration of the study (CT) or for 3 months after a 2-week severe food restricted period (sFR-Refed) at 200-× magnification. Images are representative of five rats per group. More collagen deposition (green arrows) is observed in male (M)—compared to female (F)-sFR-Refed rats. E Quantitation of collagen deposition in CT and sFR-Refed rats in the hearts of both sexes. Values are expressed as the mean ± SEM; #p < 0.05 vs. CT, same sex and *p < 0.05 vs. F, same diet by two-way ANOVA and Bonferroni post-hoc test

Fig. 4. Effect of 3 months refeeding after severe food restriction followed by ischemia/reperfusion on cardiac pathology in the isolated heart. A–H Representative sections of the left ventricle of the heart after staining with hematoxylin and eosin (H&E) in female (F) and male (M) rats maintained on a normal diet for the duration of the study (CT) or for 3 months after a 2-week severe food restricted period (sFR-Refed) with subsequent exposure of the isolated heart to a 30 min period of ischemia followed by 60 min of reperfusion (I/R) at 200× (A–D) and 1000× (E–H) magnification. Images are representative of five rats per group. Greater interstitial space (blue arrow), fiber constrictions (black box) and focal cell lysis (black circle) are more prominent in sFR-Refed + I/R rats of both sexes compared to their same sex CT + I/R groups. I Gaussian Kernel density estimates of cardiomyocyte thickness from H&E-stained hearts. The color coded vertical dashed lines represent the mean in each animal group. J The percentage of cardiomyocytes below (A, atrophied) and above (H, hypertrophied) the cardiomyocyte diameter normal (N) range (depicted by two black vertical lines). Values are expressed as…

Fig. 5. Effect of 3 months refeeding after severe food restriction followed by ischemia/reperfusion on collagen deposition in the isolated heart. A–D Representative sections of the left ventricle of the heart after staining with Masson’s trichrome in female (A and C) and male (B and D) rats maintained on a normal diet for the duration of the study (CT) or for 3 months after a 2-week severe food restricted period (sFR-Refed) with subsequent exposure of the isolated heart to a 30 min period of ischemia followed by 60 min of reperfusion (I/R) at 200× magnification. Images are representative of five rats per group. More collagen deposition (green arrows) is observed in male (M) compared to female (F)-sFR-Refed + I/R rats. E Quantitation of collagen deposition in the isolated heart of CT and sFR-Refed rats in both sexes. Values are expressed as the mean ± SEM; #p < 0.05 vs. CT, same sex and *p < 0.05 vs. F, same diet by two-way ANOVA and Bonferroni post-hoc test

Fig. 6. Effect of 3 months refeeding after severe food restriction on isolated heart function during reperfusion after ischemia. A Perfusion pressure (PP), B change in developed left-ventricular pressure (dLVP), C maximum rate of change in left ventricular pressure (Max dP/dt), D minimum rate of change in left ventricular pressure (Min dP/dt), E change in heart rate (HR), and, F percent of arrhythmias after 30 min of ischemia (I) in the basal state (B) and during the 60 min reperfusion (R) period in female (F, purple circle, red square; n = 7/group) and male (M, black circle, green square; n = 5/group) rats maintained on a normal diet for the duration of the study (CT, circle) or for 3 months after a 2-week sFR period (sFR-Refed, square). Values are expressed as the mean ± SEM; #p < 0.05 vs. CT, same timepoint, same sex and *p < 0.05 vs. F, same diet, same timepoint by two-way ANOVA mixed-model for repeated measurements and Student’s t test for individual timepoints