Fasting in vivo delays myocardial cell damage after brief periods of ischemia in the isolated working rat heart.

Abstract

To assess the effects of fasting on recovery of function and exogenous glucose metabolism after 15 minutes of total ischemia, we perfused isolated working rat hearts from fed and fasted animals. Hearts were perfused in a recirculating system with bicarbonate buffer containing glucose (10 mM). Mechanical performance, release of marker proteins for ischemic membrane damage (lactate dehydrogenase, myoglobin, citrate synthase), and the concentrations of lactate and glucose in the perfusion medium were measured serially. Tissue metabolites were also measured. Fasting raised the myocardial glycogen content by 25%. Cardiac performance of perfused hearts from fed and fasted animals was the same during the preischemic and the post-ischemic period. The time of return of function to preischemic values was significantly less in hearts from fasted rats (2.3 versus 7.8 minutes, p less than 0.025). The release of cytosolic and mitochondrial marker proteins was significantly lower in hearts from fasted rats than in hearts from fed rats. Glucose metabolic rates during control and reperfusion were unchanged for hearts from fasted rats, but decreased for hearts from fed rats during reperfusion. The adenine nucleotide content at the end of ischemia was higher in hearts from fasted animals than in hearts from fed animals. We conclude that increasing glycogen levels prior to ischemia improves recovery of function, lessens membrane damage, and prevents loss of adenine nucleotides.

Impaired Long-Chain Fatty Acid Oxidation and Contractile Dysfunction in the Obese Zucker Rat Heart

“…Previous studies have already suggested that, in normal rats, fasting overnight improves cardiac performance (23,24). Consistent with these reports, we have found that fasting in lean Zucker rats increases cardiac output.…”

Effects of 5-hydroxydecanoate and ischemic preconditioning on the ischemic-reperfused heart of fed and fasted rats

“…It has been confirmed as previously reported the protective effect of fasting on the myocardial performance in ischemic-RP hearts (10, 12,17,18,26). In addition, since the preischemic glycogen stores were higher in hearts from control fasted rats and glycogen depletion reached similar values after sustained ischemia in the fed and fasted groups, it seems evident that the amount of glycogen broken down was greater in the fasted hearts.…”

“…This finding contrast with previously reported data (17,18) but agree with another papers which showed that creatine kinase leakage as well as infarct size were similar in the fed and fasted groups (10, 26,32). From present data ir arises that the alleviation of the ischemic dysfunction in the fasted rat heart ought to be an effect exerted only on the viable myocardium.…”

Glucose for the Heart

“…79 Many other studies, however, have shown that protection of the heart against ischemic injury is related to glycogen availability. 73,81,[105][106][107][108][109] The absolute amount of glucose moieties arising from glycogen is not negligible at the onset of ischemia. In isolated perfused hearts subjected to low-flow ischemia, glycogen breakdown provides, during the first 15 minutes, about 60 mol glucose equivalents per gram dry weight, whereas during the same period, glucose uptake offers about 35 mol glucose per gram.…”