Cold acclimation of obese (ob/ob) mice: effects on skeletal muscle and bone

Obese (ob/ob) and lean mice at 4 weeks of age were housed at 23 degrees C or 14 degrees C for 4 or 8 weeks to determine effects of acclimation to mild cold on the growth of skeletal muscle, bone, and fat. Body weights at 12 weeks of age averaged 48 +/- 0.6 g and 27 +/- 1.9 g for obese mice housed at 23 degrees C and 14 degrees C and 29 +/- 0.5 g and 26 +/- 0.6 g and 26 +/- 0.6 g for lean mice housed at 23 degrees C and 14 degrees C, respectively. At 23 degrees C, muscle weights of obese mice were approximately 60% of those in lean mice. Muscles of obese mice did not grow during the first 4 weeks at 14 degrees C (4 to 8 weeks of age) but did show a small gain during the second 4 weeks (9 to 12 weeks of age) at 14 degrees C. As a result, by the end of 8 weeks at 14 degrees C, muscles of obese mice weighed only 35% to 45% as much as muscles of lean mice. Growth of the tibia and femur followed the same pattern as the muscles. Obese mice housed at 23 degrees C from 4 to 12 weeks of age contained about six times as much fat as lean mice at this age. Although exposure to 14 degrees C for 8 weeks depressed the accumulation of fat in obese mice, they still contained approximately three times the percentage body fat as lean counterparts.(ABSTRACT TRUNCATED AT 250 WORDS)