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1Author    Meinrad Boll3, LutzW D W Eberb, A.Ndreas Stampflb, Burkhard Messner3Requires cookie*
 Title    Lipogenic Enzymes of Rat Liver and Adipose Tissue. Dietary Variations and Effect of Polychlorinated Biphenyls  
 Abstract    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 [.imol/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 carbo­ hydrate: 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, G 6PD H and PGDH. The effect was dose-dependent but transient. In liver the response to PCB feeding was iden­ tical 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. 
  Reference    Z. Naturforsch. 49c, 665—678 (1994); received May 5/July 14 1994 
  Published    1994 
  Keywords    Lipogenic Enzymes, Rat Liver, Brown Adipose Tissue, Hepatocytes, Polychlorinated Biphenyls 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0665.pdf 
 Identifier    ZNC-1994-49c-0665 
 Volume    49 
2Author    M. Einrad Boll3, LutzW D W Eberb, Andreas StampflbRequires cookie*
 Title    Nutritional Regulation of the Activities of Lipogenic Enzymes of Rat Liver and Brown Adipose Tissue  
 Abstract    Nutrition-induced effects on the activity of enzymes of lipogenesis, fatty acid synthase (FAS; EC 2.3.1.85). ATP citrate lyase (ACL; 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 dehy­ drogenase (PGDH; EC 1.1.1.44) were investigated in liver and interscapular brown adipose tissue (BAT) of rats. The lipogenic enzymes could be grouped into two categories according to their response to dietary manipulations; FAS and ACL. both key enzymes of lipogenesis, responded fast and strongly to dietary manipulations. ME, G6PD H and PG D H , enzymes which also contribute to metabolic pathways other than lipogenesis, responded in a more sustained and less pronounced fashion. Feed deprivation caused the specific activities of lipogenic enzymes to decline several-fold. R efeeding of previously fasted (up to 3 days) animals increased the activities dramatically (10-to 25-fold) to far above pre-fasting levels ("overshoot"). Repetition of the fasting/refeed­ ing regimen increasingly impaired the ability of both tissues to synthesize overshooting en­ zyme activities in the subsequent refeeding period. The fasting-induced decline of the activi­ ties was prevented when sugars were provided to the animals via drinking water. The sugars displayed different effectivities; sucrose= glucose> fructose> m a lto s e » lactose. Sugars as the sole nutrient after fasting were also able to induce overshooting enzyme activities. Again, activities of FAS and ACL responded in a more pronounced fashion than the other three enzymes. Transition from feeding one diet to feeding a new diet of different composition led to adapta­ tion of the lipogenic enzym e activities to levels characteristic for the new diet. Replacing a low-carbohydrate with a high-carbohydrate diet proceeded with major alterations o f enzyme activities. TTiis process of attaining a new level took up to 20 days and involved pronounced oscillations of the specific activities. In contrast, when a high-carbohydrate diet was replaced with another diet, particular one high in fat, transition to new enzyme activities was com ­ pleted within 2 -3 days and proceeded without oscillations. All dietary manipulations caused more pronounced responses in young (35d-old) than in adult (180d-old) animals. 
  Reference    Z. Naturforsch. 51c, 859 (1996); Received August 8 1996 
  Published    1996 
  Keywords    Lipogenic Enzymes, D iet Composition, Starvation/Refeeding, Sugars, Enzyme Regulation Oscillation 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0859.pdf 
 Identifier    ZNC-1996-51c-0859 
 Volume    51 
3Author    Meinrad Bolla, LutzW D W Eberbc, A.Ndreas StampflbRequires cookie*
 Title    The Effect of y-Hexachlorocyclohexane (Lindane) on the Activities of Liver Lipogenic Enzymes and on Serum Lipids in Rats  
 Abstract    The effect of dietary y-hexachlorocyclohexane (lindane) (5 0 -3 5 0 ppm, 0 .1 7 -1 .1 9 |imol/kg chow) on the activity of enzymes of lipogenesis, viz., fatty acid synthase (FAS; EC 2.3.1.85), citrate cleavage enzyme (CCE; EC 4.1.3.8), malic enzym e (ME; EC 1.1.1.40), glucose-6-phos-phate dehydrogenase (G 6 PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (PGDH; EC 1.1.1.44), and on serum lipid levels, was investigated in livers of 35-day-old male Wistar rats. Lindane (150 ppm) caused a substantial decline of enzym e activities within the first 24 h of treatment. The decrease was transient, however, and enzyme activities subsequently recov­ ered despite continuation of lindane feeding. The recovery of enzyme activities was compara­ tively fast in the case of ME, G 6 PDH and PG D H , but very slow with FAS and CCE. A ctivities of lipogenic enzymes decrease when animals are starved, and increase much beyond prestarvation levels upon subsequent refeeding. Lindane in the refeeding diet blunted this overshoot of FAS and CCE activities in a dose-dependent manner. In contrast, activities of ME, G 6 PD H and P G D H responded to low dietary lindane concentrations with a substantial stimulation of the increase o f activity, whereas at high lindane concentrations the overshoot was inhibited. According to their responses to lindane exposure, liver lipogenic enzymes could be grouped into 2 categories with FAS and CCE representing one and ME, G 6 PDH and PG D H representing the other group. Polychlorinated biphenyls (PCBs) in the diet caused basically opposite changes of the activities of the lipogenic enzymes. Co-administration o f lindane and PCBs resulted in an apparent cancellation of effects, suggesting that lindane and PCBs affect fatty acid synthesis at opposite points. Levels of the serum triglycerides were increased significantly as a result of lindane feeding, while serum cholesterol and phospholipid levels were only slightly elevated. The increase of serum triglyceride levels that is routinely observed after refeeding o f starved animals was stimulated even more by low concentrations o f lindane in the refeeding diet, but inhibited by high concentrations. 
  Reference    Z. Naturforsch. 50c, 135 (1995); received August 9/September 16 1994 
  Published    1995 
  Keywords    Lipogenic Enzymes, Rat Liver, y-H exachlorocyclohexane (Lindane), Enzyme Regulation, Serum Lipids 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0135.pdf 
 Identifier    ZNC-1995-50c-0135 
 Volume    50