Fasting augments PCB impact on liver metabolism in anadromous arctic char.

Anadromous arctic char (Salvelinus alpinus) undertake short feeding migrations to seawater every summer and accumulate lipids, while the rest of the year is spent in fresh water where the accumulated lipid reserves are mobilized. We tested the hypothesis that winter fasting and the associated polychlorinated biphenyls' (PCBs) redistribution from lipid depots to critical tissues impair the liver metabolic capacity in these animals. Char were administered Aroclor 1254 (0, 1, 10, and 100 mg/kg body mass) orally and maintained for 4 months without feeding to mimic seasonal winter fasting, while fed groups (0 and 100 mg Aroclor 1254/kg) were maintained for comparison. A clear dose-related increase in PCB accumulation and cytochrome P4501A (CYP1A) protein content was observed in the livers of fasted fish. This PCB concentration and CYP1A response with the high dose of Aroclor were 1.5-fold and 3-fold greater in the fasted than in the fed fish, respectively. In fed fish, PCB exposure lowered liver glycogen content, whereas none of the other metabolic indicators were significantly affected. In fasted fish, PCB exposure depressed liver glycogen content and activities of glucose-6-phosphate dehydrogenase, alanine aminotransferase, lactate dehydrogenase, and phosphoenolpyruvate carboxykinase and elevated 3-hydroxyacylcoA dehydrogenase activity and glucocorticoid receptor protein expression. There were no significant impacts of PCB on heat shock protein 70 (hsp70) and hsp90 contents in either fed or fasted fish. Collectively, our study demonstrates that winter emaciation associated with the anadromous lifestyle predisposes arctic char to PCB impact on hepatic metabolism including disruption of the adaptive metabolic responses to extended fasting.     

Insignificance of Gluconeogenesis in Human Blood Platelets

Abstract. Human blood platelets contain no detectable activity of the enzymes fructose diphosphatase (EC 3. 1. 3. 11), phospho-enolpyruvate carboxykinase (EC 4. 1. 1. 32) and pyruvate carboxylase (EC 6. 4. 1. 1.). Glucose-6-phosphatase (EC 3. 1. 3. 9) activity is very low.
Phosphofructokinase present in human blood platelets, catalyzes a reaction which can be stimulated by AMP in a platelet homogenate, due to the presence of endogenous ADP and myokinase. These enzymes are responsible for the formation of fructose-6-phosphate from fructose-1, 6-diphosphate.
Pyruvate kinase (EC 2. 7. 1. 40) in human blood platelets belongs to the M-type, which is not inhibited by ATP, at least not under the conditions applied.
The results obtained indicate that gluconeogenesis in human blood platelets is not present in the way which has been established for liver and kidney.     

Roux-en-Y胃旁路术对2型糖尿病大鼠肝脏糖异生的影响

目的探讨Roux-en-Y胃旁路术对2型糖尿病大鼠肝脏糖异生的影响及意义。方法将40只GotoKakizaki（GK）大鼠按随机数字表法分为Rollx-en-Y胃旁路术组（A组,20只）和假手术组（B组,20只）。分别于术前及术后1、2、4周行口服葡萄糖耐量实验（OGYr）。并记录体质量。于术前及术后第4周测定两组大鼠糖化血红蛋白（HbAlc）水平。术后第4周处死大鼠获取肝脏组织,采用反转录聚合酶链反应和Westernblot技术检测肝脏组织葡萄糖6磷酸酶（G-6-P）、磷酸烯醇式丙酮酸激酶（PEPCK）的mRNA及蛋白相对表达量。结果术后1、2、4周,A组大鼠平均空腹血糖分别为6．5、4．9和4．7mmol／L,而B组分别为10-3、10．4和12．5mmol／L。两组比较差异均有统计学意义（均P〈0．05）;A组灌胃后2h血糖分别平均为8．3、6．4和5．5mmol／L,B组为21．4、23．8和24．7mmol／L,两组比较差异均有统计学意义（均P〈0．05）。A组术后第4周HbAlc为（6．8±1．0）％,低于B组的（7．9±0．8）％（P〈0．05）。A组术后4周肝脏G-6-P和PEPCK的mRNA相对表达较B组分别降低了21．0％和25．9％,蛋白表达水平也相应降低（均P〈0．05）。PAS染色示肝脏糖原沉积明显增多。结论Roux-en-Y胃旁路术后肝脏糖异生关键酶的mRNA相对表达和蛋白含量明显降低。肝脏糖异生减少．这可能是该术式的降糖机制之一。     

Changes in liver gluconeogenesis during the development of Walker‐256 tumour in rats

Few studies have investigated liver gluconeogenesis in cancer and there is no agreement as to whether the activity of this pathway is increased or decreased in this disease. The aim of this study was to evaluate gluconeogenesis from alanine, pyruvate and glycerol, and related metabolic parameters in perfused liver from Walker‐256 tumour‐bearing rats on days 5 (WK5 group), 8 (WK8 group) and 12 (WK12 group) of tumour development. There was reduction (P < 0.05) of liver glucose production from alanine and pyruvate in WK5, WK8 and WK12 groups, which was accompanied by a decrease (P < 0.05) in oxygen consumption. Moreover, there was higher (P < 0.05) pyruvate and lactate production from alanine in the WK5 group and a marked reduction (P < 0.05) of pyruvate and urea production from alanine in the WK12 group. In addition, liver glucose production and oxygen consumption from glycerol were not reduced in WK5, WK8 and WK12 groups. Thus the, the results show inhibition of hepatic gluconeogenesis from alanine and pyruvate, but not from glycerol, on days 5, 8 and 12 of Walker‐256 tumour development, which can be attributed to the metabolic step in which the substrate enters the gluconeogenic pathway.     

RIBOFLAVIN DEFICIENCY IN TETRAHYMENA PYRIFORMIS

Reduced lipid gluconeogenesis and formation of short chain and hydroxy fatty acids accompany reduction in the peroxisomal flavoprotein, L-alpha-hydroxy acid oxidase, in the ciliated protozoan, Tetrahymena pyriformis, made riboflavin deficient.