Genetic downregulation of AMPK-α isoforms uncovers the mechanism by which metformin decreases FA uptake and oxidation in skeletal muscle cells
Genetic downregulation of AMPK-α isoforms uncovers the mechanism by which metformin decreases FA uptake and oxidation in skeletal muscle cells
复制标题
DOI：
10.1152/ajpcell.00279.2010
复制
发表时间：
2010-12-01
影响因子：
5.5
通讯作者：
Turcotte, Lorraine P.
中科院分区：
文献类型：
--
作者：
Bogachus, Lindsey D.;Turcotte, Lorraine P.
Bogachus LD，Turcotte LP.AMPK-α亚型的基因下调揭示了二甲双胍减少骨骼肌细胞FA摄取和氧化的机制。Am J Physiol Cell Physiol 299：C1549-C1561,2010。2010年9月15日首次出版；DOI：10.1152/ajpcell.00279.2010。-已知二甲双胍改善胰岛素敏感性的部分原因是通过提高AMP激活的蛋白激酶(AMPK)活性和改变肌肉代谢。然而，对二甲双胍如何改变AMPK-α(1)与AMPK-α(2)激活的完全了解仍不清楚。为了研究这个问题，L6骨骼肌细胞在有或没有RNA干扰寡核苷酸序列的情况下下调AMPK-α(1)或AMPK-α(2)的蛋白表达，并与或不与5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside(AICAR)、二甲双胍和/或胰岛素孵育。与优先激活AMPK-α(2)的AICAR相反，二甲双胍以剂量和时间依赖的方式优先激活AMPK-α(1)。二甲双胍以剂量和时间依赖的方式增加(P<；0.05)葡萄糖摄取和质膜GLUT4。二甲双胍显著减少棕榈酸摄取(P<；0.05)和氧化(P<；0.05)，同时伴随PM CD36含量的类似下降(P<；0.05)，但对乙酰辅酶A羧化酶(ACC)的磷酸化没有影响(P>；0.05)。AICAR和二甲双胍同样增加(P<；0.05)核沉默交配型信息调节因子2同系物1(SIRT1)的活性。下调AMPK-α(1)可完全阻止二甲双胍诱导的棕榈酸酯摄取和氧化减少，但仅部分减少二甲双胍诱导的葡萄糖摄取增加。AMPK-α(2)的下调对二甲双胍诱导的葡萄糖摄取、棕榈酸酯摄取和氧化没有影响。二甲双胍诱导的SIRT1活性升高不受AMPK-α(1)或AMPK-α(2)下调的影响。我们的数据表明，在肌肉细胞中，二甲双胍对脂肪酸代谢的抑制作用是通过AMPK-α(1)的优先磷酸化实现的，并且数据表明AMPK和SIRT1之间的串扰不利于任何一种AMPK同工酶。
Bogachus LD, Turcotte LP. Genetic downregulation of AMPK-alpha isoforms uncovers the mechanism by which metformin decreases FA uptake and oxidation in skeletal muscle cells. Am J Physiol Cell Physiol 299: C1549-C1561, 2010. First published September 15, 2010; doi:10.1152/ajpcell.00279.2010.-Metformin is known to improve insulin sensitivity in part via a rise in AMP-activated protein kinase (AMPK) activity and alterations in muscle metabolism. However, a full understanding of how metformin alters AMPK-alpha(1) vs. AMPK-alpha(2) activation remains unknown. To study this question, L6 skeletal muscle cells were treated with or without RNAi oligonucleotide sequences to downregulate AMPK-alpha(1) or AMPK-alpha(2) protein expression and incubated with or without 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR) or metformin and/or insulin. In contrast to AICAR, which preferentially activated AMPK-alpha(2), metformin preferentially activated AMPK-alpha(1) in a dose-and time-dependent manner. Metformin increased (P < 0.05) glucose uptake and plasma membrane (PM) Glut4 in a dose-and time-dependent manner. Metformin significantly reduced palmitate uptake (P < 0.05) and oxidation (P < 0.05), and this was accompanied by a similar decrease (P < 0.05) in PM CD36 content but with no change in acetyl-CoA carboxylase (ACC) phosphorylation (P > 0.05). AICAR and metformin similarly increased (P < 0.05) nuclear silent mating-type information regulator 2 homolog 1 (SIRT1) activity. Downregulation of AMPK-alpha(1) completely prevented the metformin-induced reduction in palmitate uptake and oxidation but only partially reduced the metformin-induced increase in glucose uptake. Downregulation of AMPK-alpha(2) had no effect on metformin-induced glucose uptake, palmitate uptake, and oxidation. The increase in SIRT1 activity induced by metformin was not affected by downregulation of either AMPK-alpha(1) or AMPK-alpha(2). Our data indicate that, in muscle cells, the inhibitory effects of metformin on fatty acid metabolism occur via preferential phosphorylation of AMPK-alpha(1), and the data indicate that cross talk between AMPK and SIRT1 does not favor either AMPK isozyme.