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T3 treatment does not prevent myocardial dysfunction in chronically diabetic rats
R W Barbee1, R E Shepherd, A H Burns
1Department of Physiology, Louisiana State University Medical Center, New Orleans 70112.
The American Journal of Physiology
|February 1, 1988
Summary
This study shows that experimental diabetic cardiomyopathy in rats is partly due to a substrate deficiency, not solely hypothyroidism. Triiodothyronine (T3) treatment improved cardiac function when octanoate was supplied, suggesting substrate availability is key.
Area of Science:
- Cardiovascular Physiology
- Endocrinology
- Metabolic Disorders
Background:
- Diabetic cardiomyopathy is a significant complication of diabetes mellitus.
- Hypothyroidism can exacerbate cardiac dysfunction.
- The role of substrate availability in diabetic heart disease is not fully understood.
Purpose of the Study:
- To investigate the impact of triiodothyronine (T3) on cardiac function and metabolism in streptozotocin (STZ)-induced diabetic rats.
- To determine if T3 treatment can ameliorate cardiac dysfunction in diabetic rats.
- To explore the contribution of substrate deficiency to diabetic cardiomyopathy.
Main Methods:
- Isolated working heart preparation in STZ-induced diabetic rats.
- Administration of controlled-release triiodothyronine (T3) pellets.
- Perfusion with glucose alone or glucose with octanoate.
- Assessment of cardiac function and myocardial metabolism.
Main Results:
- Diabetic rats exhibited reduced heart rate and myocardial cytochrome c, with lower plasma T3 levels.
- T3 treatment did not improve cardiac function with glucose alone but enhanced it with octanoate in diabetic hearts.
- Differences in cardiac function between treated and untreated diabetic rats diminished with heart rate control.
Conclusions:
- Experimental diabetic cardiomyopathy is partly caused by substrate deficiency.
- Hypothyroidism is not the sole cause of cardiac dysfunction in this diabetic model.
- Octanoate, as an alternative substrate, can improve cardiac performance in diabetic hearts, especially with T3 treatment.