Centre for Cardiovascular and Lung Biology, Division of Medical Sciences, College of Medicine, Dentistry and Nursing, University of Dundee, Dundee, UK.
Br J Pharmacol. 2010 Oct;161(3):571-88. doi: 10.1111/j.1476-5381.2010.00898.x.
Insulin-induced Na(+) retention in the distal nephron may contribute to the development of oedema/hypertension in patients with type 2 diabetes. This response to insulin is usually attributed to phosphatidylinositol-3-kinase (PI3K)/serum and glucocorticoid-inducible kinase 1 (SGK1) but a role for protein kinase B (PKB) has been proposed. The present study therefore aimed to clarify the way in which insulin can evoke Na(+) retention.
We examined the effects of nominally selective inhibitors of PI3K (wortmannin, PI103, GDC-0941), SGK1 (GSK650394A) and PKB (Akti-1/2) on Na(+) transport in hormone-deprived and insulin-stimulated cortical collecting duct (mpkCCD) cells, while PI3K, SGK1 and PKB activities were assayed by monitoring the phosphorylation of endogenous proteins.
Wortmannin substantially inhibited basal Na(+) transport whereas PI103 and GDC-0941 had only very small effects. However, these PI3K inhibitors all abolished insulin-induced Na(+) absorption and inactivated PI3K, SGK1 and PKB fully. GSK650394A and Akti-1/2 also inhibited insulin-evoked Na(+) absorption and while GSK650394A inhibited SGK1 without affecting PKB, Akti-1/2 inactivated both kinases.
While studies undertaken using PI103 and GDC-0941 show that hormone-deprived cells can absorb Na(+) independently of PI3K, PI3K seems to be essential for insulin induced Na(+) transport. Akti-1/2 does not act as a selective inhibitor of PKB and data obtained using this compound must therefore be treated with caution. GSK650394A, on the other hand, selectively inhibits SGK1 and the finding that GSK650394A suppressed insulin-induced Na(+) absorption suggests that this response is dependent upon signalling via PI3K/SGK1.
胰岛素诱导的远端肾单位钠离子潴留可能导致 2 型糖尿病患者发生水肿/高血压。这种胰岛素反应通常归因于磷脂酰肌醇-3-激酶（PI3K）/血清和糖皮质激素诱导激酶 1（SGK1），但也有研究提出蛋白激酶 B（PKB）的作用。因此，本研究旨在阐明胰岛素引起钠离子潴留的方式。
我们研究了PI3K （wortmannin、PI103、GDC-0941）、SGK1（GSK650394A）和 PKB（Akti-1/2）的选择性抑制剂对激素剥夺和胰岛素刺激的皮质集合管（mpkCCD）细胞中钠离子转运的影响，同时通过监测内源性蛋白的磷酸化来检测 PI3K、SGK1 和 PKB 的活性。
wortmannin 显著抑制基础钠离子转运，而 PI103 和 GDC-0941 仅有很小的作用。然而，这些 PI3K 抑制剂均完全抑制胰岛素诱导的钠离子吸收并使 PI3K、SGK1 和 PKB 完全失活。GSK650394A 和 Akti-1/2 也抑制胰岛素引起的钠离子吸收，GSK650394A 抑制 SGK1 而不影响 PKB，而 Akti-1/2 使两种激酶失活。
虽然使用 PI103 和 GDC-0941 进行的研究表明，激素剥夺的细胞可以独立于 PI3K 吸收钠离子，但 PI3K 似乎对胰岛素诱导的钠离子转运是必需的。Akti-1/2 不能作为 PKB 的选择性抑制剂，因此必须谨慎对待使用该化合物获得的数据。另一方面，GSK650394A 选择性抑制 SGK1，而 GSK650394A 抑制胰岛素诱导的钠离子吸收的发现表明，这种反应依赖于 PI3K/SGK1 信号通路。
