The Effect of Cold Acclimation and Exercise Training on Cold Tolerance in Aged C57BL/6J Mice

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Abstract
We investigated whether intermittent cold acclimation and low intensity exercise training, two interventions known to improve thermoregulatory function in young rodents, enhanced cold tolerance in aged C57BL/6J mice. Mice, aged 18 to 20 months, were randomly assigned to four treatment conditions: (a) intermittent cold acclimation (CA) (50 min per day, 5 times per week for 3 weeks at 5 °C), (b) submaximal treadmill exercise (EX) (15 m min−1 for 30 min, 5 times per week for 8 weeks, (c) sequential treatment of CA+EX, and (d) control group. Mice were exposed to a 3-hr cold stress test (15 °C) prior to and following treatment. CA aged mice maintained normothermia and demonstrated significant increases in oxygen consumption and brown adipose tissue protein concentration compared with controls; enhanced cold tolerance was probably due to increased utilization of nonshivering thermogenesis. EX aged mice had elevated O2 consumption and increased skeletal muscle enzyme activity compared with controls; however, cold tolerance was not enhanced compared with CA mice. The data suggest that intermittent CA effectively reduces hypothermia during cold challenge in aged mice.