Influence of insulin on protein metabolism and cardiac glycogen in Houssay animals

Effects of dietary intake on myocardial glycogen in rats

Hearts with higher myocardial glycogen levels (MG) have improved tolerance to ischemia. The nutritional status of patients may influence MG levels and so its manipulation may be one way to delay myocardial damage during regional or global ischemia. In this study, the effects of a variety of dietary intakes were examined and correlated with MG levels in rats, grouped and fed in the following manner; Control; rat chow fed ad libitum, fasting of varying periods: 12 hr, 36 hr, 3 days, 5 days, and 7 days, diet manipulation; 4 groups pair-fed equicalorically with rat chow, chow and safflower oil, chow and safflower oil and dextrose, chow and dextrose. Daily weight change was recorded. At sacrifice, MG, myocardial DNA content, liver glycogen (LG), serum free fatty acid (FFA) were measured. It was found that fasting causes rapid elevation of MG within 12 hr, and during fasting the FFA level changes parallel with those of MG. Overall, weight gain had a positive correlation to LG and negative correlation to MG. With diet manipulation, certain substrates (dextrose), although equicaloric, resulted in greater weight gains and higher MG levels. Development of an optimum diet to augment MG and maintain good nutritional condition and to buy more time should be a useful clinical adjunct in patients suffering from unstable angina with high risk of imminent myocardial infarction and for preparing poor risk patients for cardiac surgery.