Moura M A, Kawashita N H, Brito S M, Brito M N, Kettelhut I C, Migliorini R H
Department of Biochemistry, School of Medicine, University of São Paulo, São Paulo, Brazil.
Metabolism. 2001 Dec;50(12):1493-8. doi: 10.1053/meta.2001.27197.
The effect of cold acclimation on brown adipose tissue (BAT) fatty acid synthesis was investigated in rats adapted to a high-protein, carbohydrate-free diet. At an ambient temperature (25 degrees C), rates of fatty acid synthesis in BAT from rats adapted to the high-protein diet were reduced to 27% of rats fed the balanced diet and increased markedly after cold acclimation (10 days at 4 degrees C), although the increase was smaller than in control rats. BAT weight increase induced by cold acclimation was smaller in rats fed the high-protein diet (30%) than in controls (100%). When expressed per whole tissue, maximal activities of BAT glucose-6-phosphate dehydrogenase, malic enzyme, adenosine triphosphate (ATP)-citrate lyase, and acetyl-coenzyme A carboxylase were markedly reduced in high-protein diet-adapted rats at 25 degrees C and increased after cold acclimation in BAT from the 2 groups. However, when expressed per milligram protein, only acetyl-coenzyme A carboxylase showed an increase in both controls and in rats fed the high-protein diet. G6P-dehydrogenase, malic enzyme, and ATP-citrate lyase increased (per milligram protein) only in rats adapted to the high-protein diet and actually decreased in BAT from cold-acclimated control rats. Initial (before activation) pyruvate dehydrogenase (PDH) complex activity was lower in BAT from rats fed the high-protein diet at 25 degrees C and increased in cold-acclimated rats from the 2 groups. Circulating levels of insulin decreased in the 2 groups after cold acclimation. The data suggest that the cold acclimation-induced increase in BAT lipogenesis in rats adapted to the high-protein diet was due to a restoration of sympathetic activity, which induced both BAT hyperplasia and activation of adipocyte free fatty acid (FFA) synthesis, with an important participation of acetyl-coenzyme A carboxylase and pyruvate dehydrogenase.
在适应高蛋白、无碳水化合物饮食的大鼠中，研究了冷适应对棕色脂肪组织（BAT）脂肪酸合成的影响。在环境温度为25摄氏度时，适应高蛋白饮食的大鼠BAT中脂肪酸合成速率降至喂食均衡饮食大鼠的27%，冷适应（4摄氏度下10天）后显著增加，尽管增加幅度小于对照大鼠。适应高蛋白饮食的大鼠冷适应诱导的BAT重量增加（30%）小于对照组（100%）。当按全组织计算时，适应高蛋白饮食的大鼠在25摄氏度时BAT葡萄糖-6-磷酸脱氢酶、苹果酸酶、三磷酸腺苷（ATP）-柠檬酸裂解酶和乙酰辅酶A羧化酶的最大活性显著降低，冷适应后两组大鼠的BAT中这些酶的活性均增加。然而，当按每毫克蛋白质计算时，只有乙酰辅酶A羧化酶在对照组和喂食高蛋白饮食的大鼠中均显示增加。葡萄糖-6-磷酸脱氢酶、苹果酸酶和ATP-柠檬酸裂解酶（每毫克蛋白质）仅在适应高蛋白饮食的大鼠中增加，而在冷适应的对照大鼠的BAT中实际上降低。初始（激活前）丙酮酸脱氢酶（PDH）复合物活性在25摄氏度时喂食高蛋白饮食的大鼠的BAT中较低，在两组冷适应大鼠中均增加。冷适应后两组大鼠的循环胰岛素水平均降低。数据表明，冷适应诱导的适应高蛋白饮食大鼠的BAT脂肪生成增加是由于交感神经活动的恢复，这诱导了BAT增生和脂肪细胞游离脂肪酸（FFA）合成的激活，乙酰辅酶A羧化酶和丙酮酸脱氢酶起到了重要作用。
