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Cardiac carnitine deficiency and altered carnitine transport in cardiomyopathic hamsters
Insights
Cardiomyopathy in Bio 14.6 hamsters is linked to a lifelong cardiac carnitine deficiency. This deficiency stems from a defective heart transport mechanism, not advanced disease.
Area of Science:
- Cardiology
- Biochemistry
- Animal Models
Background:
- Bio 14.6 hamsters exhibit cardiomyopathy leading to congestive heart failure.
- Previous studies indicated reduced fatty acid oxidation and carnitine levels in these hamsters' hearts.
Purpose of the Study:
- To investigate the cause of cardiac carnitine deficiency in cardiomyopathic hamsters.
- To determine if the carnitine deficiency is primary or secondary to advanced cardiomyopathy.
Main Methods:
- Analysis of cardiac and other tissue carnitine concentrations across various ages.
- Assessment of oral carnitine treatment efficacy.
- Characterization of cardiac carnitine-binding protein function.
Main Results:
- Cardiomyopathic hamsters showed carnitine deficiency throughout their lifespan.
- Other tissues maintained normal or elevated carnitine levels.
- Cardiac carnitine-binding protein exhibited impaired carnitine binding and increased dissociation.
Conclusions:
- The cardiac carnitine deficiency is a primary defect, not secondary to advanced cardiomyopathy.
- Evidence supports a defective cardiac carnitine transport mechanism in these hamsters.
- Altered cardiac carnitine transport is a key factor in hamster cardiomyopathy.
Abstract:
The Bio 14.6 hamster has a well-documented cardiomyopathy which leads to congestive heart failure. Previous work demonstrated that hearts from these hamsters have depressed fatty acid oxidation and depressed carnitine concentrations compared to those of normal hamsters. Analyses of tissue carnitine concentrations from 40 to 464 days of age demonstrate that the cardiomyopathic hamsters have a cardiac carnitine deficiency throughout life. Therefore, the carnitine deficiency is not a secondary effect of an advanced stage of the cardiomyopathy. Both the observation that other tissues of the cardiomyopathic hamster have normal or markedly elevated carnitine concentrations and the observation that oral carnitine treatment could not increase the cardiac carnitine concentrations to those of normal hamsters are consistent with the hypothesis that the cardiac carnitine deficiency is the result of a defective cardiac transport mechanism. Cardiac carnitine-binding protein (which may function in the cardiac carnitine transport mechanism) prepared from hearts of cardiomyopathic hamsters had a lower maximal carnitine binding and an increased dissociation constant for carnitine compared to the cardiac carnitine-binding protein prepared from normal hamsters. Thus, several types of data indicate that the cardiomyopathic hamster has an altered cardiac carnitine transport mechanism.