Boll M, Weber L W, Stampfl A, Messner B
Abteilung Zellchemie, National Center for Environment and Health, München, Germany.
Z Naturforsch C J Biosci. 1994 Sep-Oct;49(9-10):665-78. doi: 10.1515/znc-1994-9-1018.
The lipogenic enzymes fatty acid synthase (FAS; EC 2.3.1.85), citrate cleavage enzyme (CCE; EC 4.1.3.8), malic enzyme (ME; EC 1.1.1.40), glucose-6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (PGDH; EC 1.1.1.44) were investigated in liver and in brown adipose tissue (BAT) of Wistar rats under various dietary conditions and in the presence of 15 to 250 ppm (approximately 0.045-0.75 mumol/kg chow) polychlorinated biphenyls (PCBs). In response to refeeding starved animals, enzyme activities in both tissues increased to above normal levels and thereafter exhibited pronounced oscillations of their activities. The extent of increase depended on the carbohydrate and fat content of the diet. The lipogenic enzymes could be grouped in two categories according to their sensitivity to dietary carbohydrate: FAS and CCE responded faster to smaller changes in dietary composition, while ME, G6PDH and PGDH required larger changes and more time to respond. Diet-induced alterations of enzyme activities were of the same order of magnitude in liver and BAT. They were age-dependent, being more pronounced in young animals. Independent of the type of dietary manipulations, activities changed in a coordinate fashion, i.e., the changes of the activities of all 5 enzymes occurred at similar ratios to each other with an identical time course. Feeding PCB-containing diets resulted in a considerable increase of the activities of the lipogenic enzymes in liver, which was significantly greater with ME, G6PDH and PGDH. The effect was dose-dependent but transient. In liver the response to PCB feeding was identical in male and female animals, whereas in BAT lipogenic activities increased in females, but decreased in males. Refeeding starved animals with a PCB-containing diet led to an additional stimulation of the normal refeeding-induced increase of the enzyme activities in liver and BAT. This PCB-induced increase was 2-fold for FAS and CCE, but up to 15-fold for the other enzymes. All PCB-induced effects were significantly less pronounced in old than in young animals. In primary hepatocytes activities increased in hormone-free medium in the presence of PCBs. While activity was induced in insuline- and triiodothyronine-containing medium, this increase was significantly greater with PCBs present.
在不同饮食条件下以及存在15至250 ppm（约0.045 - 0.75 μmol/kg食物）多氯联苯（PCBs）的情况下，对Wistar大鼠肝脏和棕色脂肪组织（BAT）中的生脂酶脂肪酸合酶（FAS；EC 2.3.1.85）、柠檬酸裂解酶（CCE；EC 4.1.3.8）、苹果酸酶（ME；EC 1.1.1.40）、葡萄糖-6-磷酸脱氢酶（G6PDH；EC 1.1.1.49）和6-磷酸葡萄糖酸脱氢酶（PGDH；EC 1.1.1.44）进行了研究。对饥饿动物重新喂食后，两种组织中的酶活性均增加至正常水平以上，随后其活性出现明显波动。增加的程度取决于饮食中的碳水化合物和脂肪含量。根据生脂酶对饮食碳水化合物的敏感性可将其分为两类：FAS和CCE对饮食组成的较小变化反应更快，而ME、G6PDH和PGDH则需要更大的变化和更多时间来反应。饮食诱导的酶活性变化在肝脏和BAT中的量级相同。它们与年龄有关，在幼龄动物中更为明显。与饮食操作类型无关，酶活性以协同方式变化，即所有5种酶活性的变化以相似的比例且在相同的时间进程中发生。喂食含PCB的饮食导致肝脏中生脂酶活性显著增加，ME、G6PDH和PGDH的增加更为明显。这种效应呈剂量依赖性但具有短暂性。在肝脏中，雄性和雌性动物对PCB喂食的反应相同，而在BAT中，雌性的生脂活性增加，雄性则降低。用含PCB的饮食对饥饿动物重新喂食导致肝脏和BAT中酶活性在正常重新喂食诱导增加的基础上进一步受到刺激。PCB诱导的这种增加对于FAS和CCE为2倍，但对于其他酶高达15倍。所有PCB诱导的效应在老龄动物中比在幼龄动物中明显不那么显著。在原代肝细胞中，在无激素培养基中PCBs存在时活性增加。虽然在含胰岛素和三碘甲状腺原氨酸的培养基中活性也被诱导，但PCBs存在时这种增加更为显著。
