The effect of cold acclimation and exercise training on cold tolerance in aged C57BL/6J mice.

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 degrees 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 degrees 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.