Morabito D, Montessuit C, Rosenblatt-Velin N, Lerch R, Vallotton M B, Lang U
Division of Endocrinology and Diabetology, Department of Internal Medicine, University Hospital of Geneva, Geneva, Switzerland.
Int J Obes Relat Metab Disord. 2002 Mar;26(3):327-34. doi: 10.1038/sj.ijo.0801881.
To investigate the influence of obesity on the regulation of myocardial glucose metabolism following protein kinase C (PKC) activation in obese (fa/fa) and lean (Fa/?) Zucker rats.
Isolated hearts obtained from 17-week-old lean and obese Zucker rats were perfused with 200 nM phorbol 12-myristate 13-acetate (PMA) for different time periods prior to the evaluation of PKC and GLUT-4 translocation. For metabolic studies isolated hearts from 48 h starved Zucker rats were perfused with an erythrocytes-enriched buffer containing increased concentrations (10-100 nM) of PMA.
Immunodetectable PKC isozymes and GLUT-4 were determined by Western blots. Glucose oxidation and glycolysis were evaluated by measuring the myocardial release of 14CO2 and 3H2O from [U-14C]glucose and [5-3H]glucose, respectively.
PMA (200 nM) induced maximal translocation of ventricular PKCalpha from the cytosol to the membranes within 10 min. This translocation was 2-fold lower in the heart from obese rats when compared to lean rats. PMA also induced a significant translocation of ventricular GLUT-4 from the microsomal to the sarcolemmal fraction within 60 min in lean but not in obese rats. Rates of basal cardiac glucose oxidation and glycolysis in obese rats were approximately 2-fold lower than those of lean rats. Perfusion with increasing concentrations of PMA (10-100 nM) led to a significant decrease of cardiac glucose oxidation in lean but not in obese rats.
Our results show that in the heart of the genetically obese Zucker rat, the impairment in PKCalpha activation is in line with a diminished activation of GLUT-4 as well as with the lack of PMA effect on glucose oxidation.
研究肥胖对肥胖（fa/fa）和瘦（Fa/?） Zucker大鼠蛋白激酶C（PKC）激活后心肌葡萄糖代谢调节的影响。
从17周龄的瘦和肥胖Zucker大鼠获取离体心脏，在评估PKC和葡萄糖转运蛋白4（GLUT-4）转位之前，用200 nM佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA）灌注不同时间段。对于代谢研究，将饥饿48小时的Zucker大鼠的离体心脏用含浓度递增（10 - 100 nM）PMA的富红细胞缓冲液灌注。
通过蛋白质印迹法测定可免疫检测的PKC同工酶和GLUT-4。分别通过测量心肌从[U-14C]葡萄糖和[5-3H]葡萄糖释放的14CO2和3H2O来评估葡萄糖氧化和糖酵解。
PMA（200 nM）在10分钟内诱导心室PKCα从胞质溶胶到细胞膜的最大转位。与瘦大鼠相比，肥胖大鼠心脏中的这种转位降低了2倍。PMA还在60分钟内诱导瘦大鼠心室GLUT-4从微粒体向肌膜部分的显著转位，但肥胖大鼠未出现。肥胖大鼠基础心脏葡萄糖氧化和糖酵解速率比瘦大鼠低约2倍。用浓度递增的PMA（10 - 100 nM）灌注导致瘦大鼠心脏葡萄糖氧化显著降低，但肥胖大鼠未出现。
我们的结果表明，在遗传性肥胖Zucker大鼠的心脏中，PKCα激活受损与GLUT-4激活减弱以及PMA对葡萄糖氧化缺乏作用一致。
