Effect of cold acclimation on brown adipose tissue fatty acid synthesis in rats adapted to a high-protein, carbohydrate-free diet.
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.
Moura
M A
MA
Department of Biochemistry, School of Medicine, University of São Paulo, São Paulo, Brazil.
Kawashita
N H
NH
Brito
S M
SM
Brito
M N
MN
Kettelhut
I C
IC
Migliorini
R H
RH
D001275:ATP Citrate (pro-S)-Lyase / Q000378:metabolism; D000064:Acclimatization; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000222:Adaptation, Physiological; D002001:Adipose Tissue, Brown / Q000033:anatomy & histology / Q000378:metabolism*; D000818:Animals; D001831:Body Temperature; D003080:Cold Temperature; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004044:Dietary Proteins / Q000008:administration & dosage*; D005227:Fatty Acids / Q000096:biosynthesis*; D005954:Glucosephosphate Dehydrogenase / Q000378:metabolism; D008291:Malate Dehydrogenase / Q000378:metabolism; D008297:Male; D009929:Organ Size; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D005227:Fatty Acids; D011768:Pyruvate Dehydrogenase Complex; D008291:Malate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase; D001275:ATP Citrate (pro-S)-Lyase; D000103:Acetyl-CoA Carboxylase