Normalisation of diabetic heart pump function at decreased functional load

Aim      To study left ventricular (LV) hemodynamics in presence of decreased blood inflow to the heart as well as changes in myocardial content of energy metabolites in diabetic rats.

Material and methods  Diabetic cardiomyopathy is characterized by impaired heart contractility and by transition of cardiomyocyte energy metabolism fatty acids exclusively as a source of energy. This reduces the efficiency of energy utilization and increases the heart vulnerability to hypoxia. This study was performed on rats with type 1 diabetes mellitus induced by administration of streptozotocin (60 mg/kg). The LV pump function was studied with a catheter that allows simultaneous measurement of LV pressure and volume in each cardiac cycle.

Results Blood glucose was approximately sixfold increased at 2 weeks. Heart failure was detected with decreases in ejection fraction by 27%, minute volume by 39%, and stroke work by 41%. Systolic dysfunction was based on a decrease in LV peak ejection velocity by more than 50%. Furthermore, the LV developed pressure and contractility index were within the normal range, while 1.5 times increased arterial stiffness was the factor that hampered ejection. The sum of adenine nucleotides was decreased by 21%, the ATP content was decreased by 29%, and also creatine phosphate formation was reduced in the myocardium of diabetic rats. Lactate content in the diabetic myocardium was increased almost threefold, which indicated mobilization of aerobic glycolysis. With the reduced preload, equal diastolic volume (0.3 ml), and equal blood pressure (60 mm Hg), the diabetic heart pump function did not differ from the control.

Conclusion      In type 1 diabetes mellitus, decreases in functional load and oxygen consumption normalize the myocardial pump function with disturbed energy metabolism.

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