Department of Nephrology, The second People's Hospital, Shenzhen, The first Affiliated Hospital of Shenzhen University, Guangdong 518000, PR China; Department of Pathophysiology, China Medical University, Shenyang, Liaoning 110001, PR China.
Department of Pathophysiology, China Medical University, Shenyang, Liaoning 110001, PR China.
Metabolism. 2018 Nov;88:40-50. doi: 10.1016/j.metabol.2018.09.002. Epub 2018 Sep 17.
Zinc is intimately involved in testosterone production. Zinc transporter 8 (ZnT8) is found to be localized in insulin secretory granules as a β-cell specific Zn transporter. The effect of ZnT8 and related zinc accumulation in steroidogenesis, however, is still unknown. The present study aimed to explore whether ZnT8 plays a role in the facilitation of zinc accumulation and regulation of testosterone synthesis in testicles.
Leydig cells were isolated from the testicles of human, CD-1 suckling and ZnT8-KO mice. Zn accumulation in mitochondria was induced by hCG stimulation. Transfection of hZnT8-EGFP and RNA interfere of mZnT8 were done in MLTC-1 cells. ZnT8 expression and its co-localization with steroidogenic acute regulatory (StAR) protein were analyzed with RT-PCR, Western blot and dual-fluorescent staining protocols. Serum testosterone levels in mice were determined with chemiluminescent enzyme immunoassay.
ZnT8 was found to be presented in Leydig cells and up-regulated in suckling mouse Leydig cells and MLTC-1 cells after hCG administration, by which zinc accumulation occurred in mitochondria. ZnT8 gene silencing or knockout inhibited stimulated progesterone and testosterone production, reduced stimulated zinc accumulation and down-regulated phosphorylated steroidogenic acute regulatory (StAR) expression in Leydig cells. Furthermore, an inhibitor (H89) of PKA blocked hCG-stimulated progesterone caused by ZnT8 over-expression and zinc treatment.
The present study provided the first evidence that ZnT8 transports Zn into Leydig cell mitochondria with gonadotropin stimulation and suggests that ZnT8 may play a role in testosterone production via the PKA signaling pathway.
锌与睾酮的产生密切相关。锌转运蛋白 8（ZnT8）被发现定位于胰岛素分泌颗粒中，是一种β细胞特异性锌转运蛋白。然而，ZnT8 及其相关锌在类固醇生成中的作用尚不清楚。本研究旨在探讨 ZnT8 是否在促进睾丸中锌积累和调节睾酮合成中发挥作用。
从人、CD-1 幼鼠和 ZnT8-KO 小鼠的睾丸中分离出间质细胞。用 hCG 刺激诱导线粒体中锌的积累。在 MLTC-1 细胞中转染 hZnT8-EGFP 和 mZnT8 RNA 干扰。用 RT-PCR、Western blot 和双荧光染色方案分析 ZnT8 表达及其与类固醇急性调节蛋白（StAR）蛋白的共定位。用化学发光酶免疫分析法测定小鼠血清睾酮水平。
ZnT8 存在于间质细胞中，并在 hCG 处理后的幼鼠间质细胞和 MLTC-1 细胞中上调，导致线粒体中锌的积累。ZnT8 基因沉默或敲除抑制了孕酮和睾酮的刺激产生，减少了刺激引起的锌积累，并下调了间质细胞中磷酸化的类固醇急性调节蛋白（StAR）表达。此外，PKA 的抑制剂（H89）阻断了 ZnT8 过表达和锌处理引起的 hCG 刺激的孕酮。
本研究首次提供了证据表明，ZnT8 在促性腺激素刺激下将锌转运到间质细胞的线粒体中，提示 ZnT8 可能通过 PKA 信号通路在睾酮产生中发挥作用。
