Kawashita N H, Brito M N, Brito S R C, Moura M A F, Festuccia W T L, Garofalo M A R, Machado U F, Kettelhut I C, Migliorini R H
Department of Biochemistry, School of Medicine, University of São Paulo, São Paulo, Brazil.
Metabolism. 2002 Nov;51(11):1501-5. doi: 10.1053/meta.2002.35582.
In vivo rates of glucose uptake, insulin-responsive glucose transporter (GLUT4) content, and activities of glycolytic enzymes were determined in brown adipose tissue (BAT) from rats adapted to a high-protein, carbohydrate-free (HP) diet. Adaptation to the HP diet resulted in marked decreases in BAT glucose uptake and in GLUT4 content. Replacement of the HP diet by a balanced control diet for 24 hours restored BAT glucose uptake to levels above those in rats fed the control diet, with no changes in GLUT4 levels in 4 of 5 animals examined. BAT denervation of rats fed the control diet induced a 50% reduction in glucose uptake, but did not significantly affect the already markedly reduced BAT hexose uptake in HP diet-fed rats. It is suggested that the pronounced decrease in BAT glucose uptake in these animals is due to the combined effects of the HP diet-induced reductions in plasma insulin levels and in BAT sympathetic activity. Adaptation to the HP diet was accompanied by decreased activities of hexokinase, phosphofructo-1-kinase, and pyruvate kinase (PK). The activity of BAT PK in HP diet-fed rats was reduced to about 50% of controls, and approached normal levels 24 hours after diet reversion. BAT denervation induced a small (15%) decrease in BAT PK activity in control rats, but did not affect the activity of the enzyme in HP diet-adapted rats. Also, denervation did not interfere with the restoration of PK activity induced by diet substitution. Treatment with anti-insulin serum resulted in an almost 50% reduction in PK activity in both innervated and denervated BAT from rats fed the control diet, but caused a much smaller ( thick approximate 20%) decrease in BAT from HP diet-fed rats. Furthermore, anti-insulin serum administration completely suppressed the restoration of BAT PK activity induced by diet reversion. These data suggest that, differently from glucose uptake, BAT PK activity is predominantly controlled by hormonal/metabolic factors.
测定了适应高蛋白、无碳水化合物（HP）饮食的大鼠棕色脂肪组织（BAT）中的体内葡萄糖摄取率、胰岛素反应性葡萄糖转运体（GLUT4）含量以及糖酵解酶的活性。适应HP饮食导致BAT葡萄糖摄取和GLUT4含量显著降低。用平衡对照饮食替代HP饮食24小时后，BAT葡萄糖摄取恢复到高于喂食对照饮食大鼠的水平，在所检查的5只动物中有4只的GLUT4水平没有变化。对喂食对照饮食的大鼠进行BAT去神经支配导致葡萄糖摄取减少50%，但对喂食HP饮食的大鼠中已经显著降低的BAT己糖摄取没有显著影响。提示这些动物中BAT葡萄糖摄取的显著降低是由于HP饮食导致的血浆胰岛素水平和BAT交感神经活性降低的联合作用。适应HP饮食伴随着己糖激酶、磷酸果糖-1-激酶和丙酮酸激酶（PK）活性的降低。喂食HP饮食的大鼠中BAT PK的活性降低到对照的约50%，饮食恢复24小时后接近正常水平。BAT去神经支配在对照大鼠中导致BAT PK活性小幅（15%）降低，但不影响适应HP饮食大鼠中该酶的活性。此外，去神经支配不干扰饮食替代诱导的PK活性恢复。用抗胰岛素血清处理导致喂食对照饮食的大鼠的去神经和未去神经BAT中的PK活性降低近50%，但在喂食HP饮食的大鼠的BAT中导致的降低要小得多（约20%）。此外，给予抗胰岛素血清完全抑制了饮食恢复诱导的BAT PK活性恢复。这些数据表明，与葡萄糖摄取不同，BAT PK活性主要受激素/代谢因素控制。
