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Moura, MA, Kawashita, NH, Brito, SM, Brito, MN, Kettelhut, IC and Migliorini, RH (2001) Effect of cold acclimation on brown adipose tissue fatty acid synthesis in rats adapted to a high-protein, carbohydrate-free diet. Metab. Clin. Exp. 50:1493-8

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.

PubMed Online version:10.1053/meta.2001.27197

ATP Citrate (pro-S)-Lyase/metabolism; Acclimatization; Acetyl-CoA Carboxylase/metabolism; Adaptation, Physiological; Adipose Tissue, Brown/anatomy & histology; Adipose Tissue, Brown/metabolism; Animals; Body Temperature; Cold Temperature; Dietary Carbohydrates/administration & dosage; Dietary Proteins/administration & dosage; Fatty Acids/biosynthesis; Glucosephosphate Dehydrogenase/metabolism; Malate Dehydrogenase/metabolism; Male; Organ Size; Pyruvate Dehydrogenase Complex/metabolism; Rats; Rats, Wistar