The accumulation of triglycerides in the myocardium of nonketotic and overtly ketotic diabetic rats was studied. There was no increase in heart triglycerides of nonketotic rats taken off insulin treatment, although the rats exhibited several indices of diabetes. In nonketotic diabetic rats untreated with insulin, myocardial triglycerides repeatedly increased and declined to control levels.

In severely ketotic rats, heart triglycerides increased about threefold and did not decline with time. In order to understand the mechanism of increase in myocardial triglycerides in ketotic diabetes, the biosynthesis of triglycerides was studied with heart homogenates. The total esterification of sn-glycero-3-phosphate was unaltered, but the synthesis of diglycerides and triglycerides was increased in the myocardium of the ketotic rat. On treatment of the diabetic rats with insulin, the synthesis of di- and triglycerides in heart homogenates reverted to control values. Thus the results of the present study demonstrate that (1) a persistent increase in myocardial triglyceride content was observed only in the ketotic diabetic rat and (2) increased synthesis of triglycerides is a factor in its accumulation in the myocardium of the ketotic rat.