Mitotic Activity in Mice is Suppressed by Energy Restriction-Induced Torpor

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Abstract
We monitored core body temperatures by telemetry in energy-restricted (201 kJ/wk) and control (397 kJ/wk) C57BL/6 and SHN/C3H F1 mice to determine whether torpor may be involved in the suppression of mitotic activities resulting from energy restriction. The energy restriction regimen employed inhibited the development of cancer and greatly extended longevity in both these mouse strains. Male and female C57BL/6 mice subjected to energy restriction from 4 wk of age and tested at 3 mo of age became torporific (body temperature 35°C). Energy restriction also induced torpor in 3- and 13-mo-old SHN/C3H F1 female mice, whereas 3-, 13- and 24-mo-old control mice were euthermic. Energy restriction decreased mitotic activities to ∼30% of control values in both jejunum and epidermis in 3-mo-old female C57BL/6 mice maintained at 20–22°C. However, this suppression of mitotic activities was antagonized by housing the energy-restricted mice at 30°C for 2 wk, indicating that torpor plays a substantial role in suppressing mitotic activities in energy-restricted mice.