BACKGROUND AND PURPOSE Catechins, biologically active polyphenols in green tea, are known to have a protective effect against cardiovascular diseases. In this study, we investigated direct actions of green tea catechins on cardiac muscle function to explore their uses as potential drugs for cardiac muscle disease. EXPERIMENTAL APPROACH The effects of catechins were systematically investigated on the force-pCa relationship in skinned cardiac muscle fibres to determine their direct effects on cardiac myofilament contractility. The mechanisms of action of effective catechins were investigated using troponin exchange techniques, quartz crystal microbalance, nuclear magnetic resonance and a transgenic mouse model. KEY RESULTS (-)-Epicatechin-3-gallate (ECg) and (-)-epigallocatechin-3-gallate (EGCg), but not their stereoismers (-)-catechin-3-gallate and (-)-gallocatechin-3-gallate, decreased cardiac myofilament Ca 2+ sensitivity probably through its interaction with cardiac troponin C. EGCg restored cardiac output in isolated working hearts by improving diastolic dysfunction caused by increased myofilament Ca 2+ sensitivity in a mouse model of hypertrophic cardiomyopathy. CONCLUSIONS AND IMPLICATIONS The green tea catechins, ECg and EGCg, are Ca 2+ desensitizers acting through binding to cardiac troponin C. These compounds might be useful compounds for the development of therapeutic agents to treat the hypertrophic cardiomyopathy caused by increased Ca 2+ sensitivity of cardiac myofilaments.
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