Low carbohydrate diet reduces myocardial glycogen stores and increases myocardial injury following ischemia‐reperfusion

Abstract

Low carbohydrate diets (LCDs) are popular for weight loss, but the safety of such diets is unknown. Myocardial glycogen may be an important energy source during ischemia, when circulating energy substrate and O2 supplies are reduced. We hypothesized that LCD lowers cardiac glycogen and increases cardiac injury during ischemia and reperfusion. Rats were fed LCD (60% kcal from fat/30% protein/10% carbohydrate) or a low fat diet (LFD; 16%/19%/65%) for 2 weeks (N=18 each diet). 6 from each group were sacrificed for biochemical analysis, 6 were subjected to 30 min of low flow ischemia (LFI; 0.3ml/min), and 6 to a 60 min reperfusion protocol following 30 min of LFI after hearts were isolated and perfused with a physiologic perfusion mixture. LCD led to significant increase of circulating free fatty acids, 3-hydroxybutyrate and decrease in insulin, and a decrease in myocardial and liver glycogen (Fig B). LCD resulted in impaired left ventricular performance during LFI, with worsened ischemic contracture and increased total lactate dehydrogenase (LDH) release (Fig. A). Cardiac glycogen was lower after LFI (0.42±0.04 and 0.44±0.02 mg/g tissue; P < 0.05 vs. pre-LFI). These results demonstrate that LCD lowers cardiac glycogen and increases myocardial injury following ischemia-reperfusion, and suggest that glycogen stores play a critical role in prevention of ischemic injury. Figure A and BOpen in figure viewerPowerPoint A: Total LDH release during LFI and reperfusion. B: Glycogen content in myocardium and liver (mg glucose/g wet tissue weight). ∗ P<0.05 vs. LFD.