In vivo activating transcription factor 3 silencing ameliorates the AMPK compensatory effects for ER stress-mediated beta-cell dysfunction during the progression of type-2 diabetes

Abstract

In obese Zucker diabetic fatty (ZDF) rats, ER stress is associated with insulin resistance and pancreatic beta-cell dysfunction: however the exact mechanisms by which ER stress drives type-2 diabetes remain uncertain. Here, we investigated the role of ATF3 on the preventive regulation of AMPK against ER stress-mediated beta-cell dysfunction during the end-stage progression of hyperglycemia in ZDF rats. The impaired glucose metabolism and beta-cell dysfunction were significantly increased in late-diabetic phase 19-week-old ZDF rats. Although AMPK phosphorylation reduced in 6- and 12-week-old ZDF rats was remarkably increased at 19 weeks, the increases of lipogenice genes, ATF3, and ER stress or ROS-mediated beta-cell dysfunction were still remained, which were attenuated by in vivo-injection of chemical chaperon tauroursodeoxycholate (TUDCA), chronic AICAR, or antioxidants. ATF3 did not directly affect AMPK phosphorylation, but counteracts the preventive effects of AMPK for high glucose-induced beta-cell dysfunction. Moreover, knockdown of ATF3 by delivery of in vivo-jetPEI ATF3 siRNA attenuated ER stress-mediated beta-cell dysfunction and enhanced the beneficial effect of AICAR. Our data suggest that ATF3 may play as a counteracting regulator of AMPK and thus promote beta-cell dysfunction and the development of type-2 diabetes and could be a potential therapeutic target in treating type-2 diabetes. (C) 2013 Elsevier Inc. All rights reserved.