Short-term caloric restriction and regulatory proteins of apoptosis in heart, skeletal muscle and kidney of Fischer 344 rats.

Long-term caloric restriction reduces oxidative stress, increases mean and maximum lifespan in rodents and tends to enhance apoptosis, particularly in the liver. We investigated the effect of short-term (2 months) caloric restriction (40% reduction) in 6-month-old male Fischer 344 rats on various indicators of apoptosis (caspase-3, -7, -12, the inhibitor of apoptosis protein XIAP and cytoplasmic histone-associated DNA fragments) in the post-mitotic heart and gastrocnemius muscle, and the kidney that contains mitotic cells. Short-term caloric restriction significantly reduced body mass (30%), gastrocnemius muscle mass (22%), heart mass (25%) and kidney mass (32%) compared to ad libitum controls. The levels of procaspase-3 in gastrocnemius muscle and caspase-3 in kidney were significantly lower in the caloric restricted than in the ad libitum fed group. While caloric restriction did not alter DNA fragmentation levels (indicative of apoptosis), differences did exist amongst tissues with significantly elevated levels of fragmentation in the kidney compared to the heart and gastrocnemius muscle and significantly higher levels in the heart compared to gastrocnemius muscle. No differences were observed between groups in the levels of procaspase-7 or -12 or in XIAP (an endogenous inhibitor of apoptosis, particularly of caspase-3 and -7) in any tissue. The active forms of caspase-7 and -12 were present only in the kidney. These findings suggest that while the rate of apoptosis was higher in the kidney, which contains mitotic cells, compared to the post-mitotic heart and gastrocnemius muscle, short-term caloric restriction did not enhance the apoptosis rate in any tissue measured.