Decreased cellular proliferation by energy restriction is recovered by increasing housing temperature in rats

We investigated the effects of life-prolonging energy restriction (ER) on body temperature (BT) and cellular proliferation in rats. Animals were fed either a control diet (C: 220 kJ/day) or an ER diet (110 kJ/day) from 7 weeks of age, and were housed at 20-22 degrees C. Another group of animals, fed on the ER diet, were transferred from 20-22 degrees C to a room at 30 degrees C (ER + I) at 20 weeks of age. The core body temperatures in individual animals were recorded over a 3-day period between 20 and 24 weeks of age. Cellular proliferation rates were quantitated by labeling S phase cells in the jejunum, epidermis, pituitary, and lung with bromodeoxy-uridine at 24 weeks of age. Long-term ER reduced the mean BT by 1 degree C, and reduced cellular proliferation in the jejunum, epidermis, pituitary, and lung. At 30 degrees C, the inhibitions were partially lifted in the examined organs except in the pituitary. Therefore, decreased cellular proliferation in the various organs after long-term ER in rats is lifted as it is in mice.