Department of Biological Sciences, University of Southern California, Los Angeles, CA 90089-0652, USA.
J Appl Physiol (1985). 2011 Jul;111(1):125-34. doi: 10.1152/japplphysiol.00807.2010. Epub 2011 May 5.
AMP-activated protein kinase (AMPK) is a fuel sensor in skeletal muscle with multiple downstream signaling targets that may be triggered by increases in intracellular Ca(2+) concentration ([Ca(2+)]). The purpose of this study was to determine whether increases in intracellular [Ca(2+)] induced by caffeine act solely via AMPKα(2) and whether AMPKα(2) is essential to increase glucose uptake, fatty acid (FA) uptake, and FA oxidation in contracting skeletal muscle. Hindlimbs from wild-type (WT) or AMPKα(2) dominant-negative (DN) transgene mice were perfused during rest (n = 11), treatment with 3 mM caffeine (n = 10), or muscle contraction (n = 11). Time-dependent effects on glucose and FA uptake were uncovered throughout the 20-min muscle contraction perfusion period (P < 0.05). Glucose uptake rates did not increase in DN mice during muscle contraction until the last 5 min of the protocol (P < 0.05). FA uptake rates were elevated at the onset of muscle contraction and diminished by the end of the protocol in DN mice (P < 0.05). FA oxidation rates were abolished in the DN mice during muscle contraction (P < 0.05). The DN transgene had no effect on caffeine-induced FA uptake and oxidation (P > 0.05). Glucose uptake rates were blunted in caffeine-treated DN mice (P < 0.05). The DN transgene resulted in a greater use of intramuscular triglycerides as a fuel source during muscle contraction. The DN transgene did not alter caffeine- or contraction-mediated changes in the phosphorylation of Ca(2+)/calmodulin-dependent protein kinase I or ERK1/2 (P > 0.05). These data suggest that AMPKα(2) is involved in the regulation of substrate uptake in a time-dependent manner in contracting muscle but is not necessary for regulation of FA uptake and oxidation during caffeine treatment.
AMP 激活的蛋白激酶(AMPK)是骨骼肌中的燃料传感器,具有多个下游信号靶标,这些靶标可能会因细胞内 Ca(2+)浓度 ([Ca(2+)]升高而被触发。本研究旨在确定咖啡因引起的细胞内 [Ca(2+)]增加是否仅通过 AMPKα(2)起作用,以及 AMPKα(2)是否对增加收缩骨骼肌中的葡萄糖摄取、脂肪酸 (FA)摄取和 FA 氧化是必需的。在休息时(n = 11)、用 3 mM 咖啡因处理时(n = 10)或肌肉收缩时(n = 11),对来自野生型 (WT)或 AMPKα(2)显性负 (DN)转基因小鼠的后肢进行灌注。在整个 20 分钟的肌肉收缩灌注期间,揭示了葡萄糖和 FA 摄取的时间依赖性效应(P < 0.05)。在肌肉收缩期间,DN 小鼠的葡萄糖摄取率直到方案的最后 5 分钟才增加(P < 0.05)。FA 摄取率在肌肉收缩开始时升高,并在 DN 小鼠的方案结束时降低(P < 0.05)。在肌肉收缩期间,DN 小鼠的 FA 氧化率被消除(P < 0.05)。DN 转基因对咖啡因诱导的 FA 摄取和氧化没有影响(P > 0.05)。在咖啡因处理的 DN 小鼠中,葡萄糖摄取率受到抑制(P < 0.05)。DN 转基因导致在肌肉收缩期间更多地将肌肉内甘油三酯用作燃料来源。DN 转基因没有改变咖啡因或收缩介导的 Ca(2+)/钙调蛋白依赖性蛋白激酶 I 或 ERK1/2 的磷酸化变化(P > 0.05)。这些数据表明,AMPKα(2) 参与调节收缩肌肉中底物摄取的时间依赖性方式,但在咖啡因处理期间调节 FA 摄取和氧化不是必需的。