A role for ATP-citrate lyase, malic enzyme, and pyruvate/citrate cycling in glucose-induced insulin secretion
A role for ATP-citrate lyase, malic enzyme, and pyruvate/citrate cycling in glucose-induced insulin secretion
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DOI：
10.1074/jbc.m707294200
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发表时间：
2007-12-07
影响因子：
4.8
通讯作者：
Prentki, Marc
中科院分区：
文献类型：
--
作者：
Guay, Claudiane;Madiraju, S. R. Murthy;Prentki, Marc
在胰腺β细胞中，葡萄糖代谢和丙酮酸循环过程中产生的代谢偶联因子有助于调节胰岛素分泌。丙酮酸/柠檬酸盐在线粒体膜上的循环导致丙二酰辅酶a和NADPH这两种候选偶联因子的产生。为了研究丙酮酸/柠檬酸循环对葡萄糖诱导胰岛素分泌（GIIS）的影响，在INS 832/13细胞中，通过药理抑制剂和/或RNA干扰（RNAi）技术抑制了循环的不同步骤：线粒体柠檬酸输出、atp -柠檬酸裂解酶（ACL）和细胞质苹果酸酶（ME1）。二羧酸盐和三羧酸盐载体的抑制剂正丁基丙二酸盐和1,2,3-苯三羧酸盐分别降低了GIIS，表明三羧酸盐和二羧酸盐在葡萄糖作用下的线粒体运输的重要性。为了直接检测ACL和ME1在GIIS中的作用，我们使用小发夹rna （small hairpinRNA, shRNA）选择性地降低转染INS 832/13细胞中ACL或ME1的表达。shRNA-ACL使ACL蛋白水平降低67%，同时伴有GIIS的降低。ACL的RNAi敲低会影响GIIS的扩增/ k - atp非依赖性通路。ACL抑制剂radicicol也减少了GIIS。shRNA-ME1使ME1活性降低62%，并降低GIIS。RNAi抑制ACL或ME1均不影响葡萄糖氧化。然而，由于丙二酰辅酶a的形成需要ACL， shRNA-ACL抑制ACL表达会减少葡萄糖向棕榈酸盐的掺入，增加INS 832/13细胞中的脂肪酸氧化。综上所述，这些结果强调了丙酮酸/柠檬酸循环在胰腺β细胞代谢信号传导和GIIS调节中的重要性。
In pancreatic beta-cells, metabolic coupling factors generated during glucose metabolism and pyruvate cycling through anaplerosis/cataplerosis processes contribute to the regulation of insulin secretion. Pyruvate/citrate cycling across the mitochondrial membrane leads to the production of malonyl-CoA and NADPH, two candidate coupling factors. To examine the implication of pyruvate/citrate cycling in glucose-induced insulin secretion (GIIS), different steps of the cycle were inhibited in INS 832/13 cells by pharmacological inhibitors and/or RNA interference (RNAi) technology: mitochondrial citrate export, ATP-citrate lyase (ACL), and cytosolic malic enzyme (ME1). The inhibitors of the di- and tri-carboxylate carriers, n-butylmalonate and 1,2,3-benzenetricarboxylate, respectively, reduced GIIS, indicating the importance of transmitochondrial transport of tri-and dicarboxylates in the action of glucose. To directly test the role of ACL and ME1 in GIIS, small hairpinRNA (shRNA) were used to selectively decrease ACL or ME1 expression in transfected INS 832/13 cells. shRNA-ACL reduced ACL protein levels by 67%, and this was accompanied by a reduction in GIIS. The amplification/K-ATP-independent pathway of GIIS was affected by RNAi knockdown of ACL. The ACL inhibitor radicicol also curtailed GIIS. shRNA-ME1 reduced ME1 activity by 62% and decreased GIIS. RNAi suppression of either ACL or ME1 did not affect glucose oxidation. However, because ACL is required for malonyl-CoA formation, inhibition of ACL expression by shRNA-ACL decreased glucose incorporation into palmitate and increased fatty acid oxidation in INS 832/13 cells. Taken together, the results underscore the importance of pyruvate/citrate cycling in pancreatic beta-cell metabolic signaling and the regulation of GIIS.