Abstract
This study examined the effects of age and dietary manipulations on the cardiac myosin isozyme composition of male Fischer 344 rats. In hearts from ad libitum-fed rats, aged 6-24 months, the myosin isozyme profile shifted with age from the fast, V1, to the slow, V3, isoform. Life-long food restriction (FR) (60% of ad libitum intake) as well as short-term FR (4 months) initiated at 16 months of age enhanced the age-related shift. Isocaloric reduction in the carbohydrate consumption of the rat from 2/3 to 1/3 of total calories had no effect on the isozyme profile, suggesting that FR acts via a decrease in calorie intake alone. The effect of FR on the cardiac myosin isozyme composition reported here shares several characteristics with the well-known effect of FR on life span extension, i.e., it (a) persists as long as FR is applied (life span extension is proportional to FR duration), (b) depends upon calorie reduction rather than a decrease in a specific dietary component, and (c) can be induced even when FR is initiated later in life. Suggesting that alterations in cardiac performance may be involved, the results may provide some clue as to the mechanism by which FR retards the aging processes.
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