Myocardial remodelling in left ventricular atrophy induced by caloric restriction

Changes in body weight due to changes in food intake are reflected by corresponding changes in the cardiac phenotype. Despite a growing body of literature on cardiac hypertrophy associated with obesity, little is known on the atrophic remodelling of the heart associated with calorie restriction. We hypothesized that, besides the cardiomyocyte compartment, capillaries and nerve fibres are involved in the atrophic process. C57Bl6 mice were kept on normal diet (control group) or at a calorie-restricted diet for 3 or 7 days (n = 5 each). At the end of the protocol, mice were killed and the hearts were processed for light and electron microscopic stereological analysis of cardiomyocytes, capillaries and nerve fibres. Body, heart and left ventricular weight were significantly reduced in the calorie-restricted animals at 7 days. Most morphological parameters were not significantly different at 3 days compared with the control group, but at 7 days most of them were significantly reduced. Specifically, the total length of capillaries, the volume of cardiomyocytes as well as their subcellular compartments and the interstitium were proportionally reduced during caloric restriction. No differences were observed in the total length or the mean diameter of axons between the cardiomyocytes. Our data indicate that diet-induced left ventricular atrophy leads to a proportional atrophic process of cardiomyocytes and capillaries. The innervation is not involved in the atrophic process.