Zhang S-J, Sandström M E, Aydin J, Westerblad H, Wieringa B, Katz A
Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
Acta Physiol (Oxf). 2008 Mar;192(3):413-20. doi: 10.1111/j.1748-1716.2007.01767.x. Epub 2007 Oct 31.
Recently it was reported that adenylate kinase-1 knockout mice (AK(-/-)) exhibit elevated rates of glucose uptake following repeated contractions and hypoxia, but the mechanism was not investigated. The purpose of the present study was to measure the changes in glucose transport and AMP-activated protein kinase (AMPK) phosphorylation/activity following repeated contractions in isolated muscles from AK(-/-) mice.
Extensor digitorum longus muscles underwent an intense stimulation protocol that decreased force to less than 10% of initial by the end of 10 min. Glucose uptake was measured with 2-deoxy-D-[1,2-(3)H]glucose.
Muscle glucose uptake in the basal state was identical between control and AK(-/-) mice and increased twofold in both groups during contraction. The general antioxidant: N-acetylcysteine, decreased contraction-mediated glucose uptake by 30% in both groups. AMPK activity and phosphorylation were similar in the two groups in the basal state and, surprisingly, after contraction as well (approximately threefold increase). Both groups exhibited marked decreases in adenosine triphosphate following contraction (60-70% depletion), which coincided with stoichiometric increases in the content of inosine monophosphate, an indirect marker of AMP production. Adenylate kinase activity averaged 2081 +/- 106 micromol min(-1) (g dry wt)(-1) for control and 37 +/- 10 for AK(-/-) muscles; the activity in the AK(-/-) muscle is likely accounted for by isoforms other than AK1.
In conclusion, AK(-/-) mice have a normal capacity for contraction-mediated glucose uptake. This appears to occur via increases in AMP and reactive oxygen species that result in the activation of AMPK.
最近有报道称，腺苷酸激酶-1基因敲除小鼠（AK(-/-)）在反复收缩和缺氧后葡萄糖摄取率升高，但具体机制尚未研究。本研究旨在测量AK(-/-)小鼠离体肌肉反复收缩后葡萄糖转运和AMP激活的蛋白激酶（AMPK）磷酸化/活性的变化。
对趾长伸肌进行强烈刺激方案，在10分钟结束时使力量降至初始值的10%以下。用2-脱氧-D-[1,2-(3)H]葡萄糖测量葡萄糖摄取。
对照组和AK(-/-)小鼠基础状态下的肌肉葡萄糖摄取相同，两组在收缩期间均增加了两倍。一般抗氧化剂：N-乙酰半胱氨酸，使两组收缩介导的葡萄糖摄取降低30%。两组基础状态下AMPK活性和磷酸化相似，令人惊讶的是，收缩后也相似（增加约三倍）。两组收缩后三磷酸腺苷均显著降低（消耗60-70%），这与单磷酸肌苷含量的化学计量增加一致，单磷酸肌苷是AMP产生的间接标志物。对照组腺苷酸激酶活性平均为2081±106微摩尔·分钟(-1)·（克干重）(-1)，AK(-/-)肌肉为37±10；AK(-/-)肌肉中的活性可能由AK1以外的同工型负责。
总之，AK(-/-)小鼠具有正常的收缩介导的葡萄糖摄取能力。这似乎是通过AMP和活性氧的增加导致AMPK激活而发生的。
