Cold acclimation of obese ( [formula omitted]) mice: Effects on energy balance

Abstract

Obese ( ob ob ) and lean mice at 4 weeks of age were housed at 23°C or 14°C for 4 to 8 weeks to examine effects of acclimation to mild cold on energy balance. Energy intake of young lean mice increased by about 50% when housed at 14°C, but energy intake of cold-acclimated obese mice increased by only 8%. Efficiency of energy retention (ratio of energy gain to energy intake) in obese mice declined from 22% ± 1.2% at 23°C to 10% ± 1.8% after 4 weeks at 14°C. Lean mice exhibited a less pronounced response to temperature; their efficiency of energy retention declined from 7% ± 1.3% at 23°C to 4% ± 2.2% after 4 weeks at 14°C. After 8 weeks of cold exposure, body weights and efficiency of energy retention became equal in obese and lean mice. Calculated heat production of cold-acclimated obese and lean mice was 40% cigher than that of respective controls. Obese mice reacclimated to 23°C after being kept for 4 weeks at 14°C consumed the same amount of energy and were 16% more efficient than obese maintained at 23°C; reacclimated lean mice consumed 12% more energy but were 53% less efficient than lean mice maintained at 23°C. The results indicate that obese mice are able to increase heat production and markedly reduce their efficiency of energy retention when acclimated to mild cold but that they, unlike lean mice, rapidly revert to a high efficiency of energy retention after 4 weeks of reacclimation to 23°C.