The number of cardiac myocytes in the hypertrophic and hypotrophic left ventricle of the obese and calorie-restricted mouse heart |
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Authors: | Julia Schipke Ewgenija Banmann Sandeep Nikam Robert Voswinckel Karin Kohlstedt Annemarieke E Loot Ingrid Fleming Christian Mühlfeld |
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Institution: | 1. Department of Lung Development and Remodelling, Max‐Planck‐Institute for Heart and Lung Research, , Bad Nauheim, Germany;2. Institute for Vascular Signalling, Centre for Molecular Medicine, Goethe University Frankfurt, , Frankfurt am Main, Germany;3. Institute of Functional and Applied Anatomy, Hannover Medical School, , Hannover, Germany;4. Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), Member of the German Center for Lung Research (DZL), , Hannover, Germany;5. Cluster of Excellence REBIRTH (From Regenerative Biology to Reconstructive Therapy), , Hannover, Germany |
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Abstract: | Changes in body mass due to varying amounts of calorie intake occur frequently with obesity and anorexia/cachexia being at opposite sides of the scale. Here, we tested whether a high-fat diet or calorie restriction (CR) decreases the number of cardiac myocytes and affects their volume. Ten 6–8-week-old mice were randomly assigned to a normal (control group, n = 5) or high-fat diet (obesity group, n = 5) for 28 weeks. Ten 8-week-old mice were randomly assigned to a normal (control group, n = 5) or CR diet (CR group, n = 5) for 7 days. The left ventricles of the hearts were prepared for light and electron microscopy, and analysed by design-based stereology. In CR, neither the number of cardiac myocytes, the relationship between one- and multinucleate myocytes nor their mean volume were significantly different between the groups. In contrast, in the obese mice we observed a significant increase in cell size combined with a lower number of cardiomyocytes (P < 0.05 in the one-sided U-test) and an increase in the mean number of nuclei per myocyte. The mean volume of myofibrils and mitochondria per cardiac myocyte reflected the hypertrophic and hypotrophic remodelling in obesity and CR, respectively, but were only significant in the obese mice, indicating a more profound effect of the obesity protocol than in the CR experiments. Taken together, our data indicate that long-lasting obesity is associated with a loss of cardiomyocytes of the left ventricle, but that short-term CR does not alter the number of cardiomyocytes. |
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Keywords: | calorie restriction cell death design-based stereology myocardium obesity |
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