Liver-specific ablation of insulin-degrading enzyme causes hepatic insulin resistance and glucose intolerance, without affecting insulin clearance in mice

The study was partially presented as a poster in the 53rd Annual Meeting of the European Association for the Study of Diabetes, Lisbon 2017.
The role of insulin-degrading enzyme (IDE), a metalloprotease with high affinity for insulin, in insulin clearance remains poorly understood. OBJECTIVE: This study aimed to clarify whether IDE is a major mediator of insulin clearance, and to define its role in the etiology of hepatic insulin resistance.
[Methods] We generated mice with liver-specific deletion of Ide (L-IDE-KO) and assessed insulin clearance and action.
[Results] L-IDE-KO mice exhibited higher (~20%) fasting and non-fasting plasma glucose levels, glucose intolerance and insulin resistance. This phenotype was associated with ~30% lower plasma membrane insulin receptor levels in liver, as well as ~55% reduction in insulin-stimulated phosphorylation of the insulin receptor, and its downstream signaling molecules, AKT1 and AKT2 (reduced by ~40%). In addition, FoxO1 was aberrantly distributed in cellular nuclei, in parallel with up-regulation of the gluconeogenic genes Pck1 and G6pc. Surprisingly, L-IDE-KO mice showed similar plasma insulin levels and hepatic insulin clearance as control mice, despite reduced phosphorylation of the carcinoembryonic antigen-related cell adhesion molecule 1, which upon its insulin-stimulated phosphorylation, promotes receptor-mediated insulin uptake to be degraded.
[Conclusion] IDE is not a rate-limiting regulator of plasma insulin levels in vivo.
This work was supported by grants from the Ministerio de Economía, Industria y Competitividad: SAF2014-58702-C2-1-R and SAF2016-77871-C2-1-R to ICC; SAF2014-58702-C2-2-R and SAF2016-77871-C2-2-R to GP; supported by the EFSD European Research Programme on New Targets for Type 2 Diabetes supported by an educational research grant from MSD to ICC and GP; the National Institutes of Health: R01-DK054254, R01-DK083850 and RO1-HL-112248 to SMN, and R01-GM115617 to MAL; and the American Diabetes Association: Career Development Award 7-11-CD-13 to MAL.