Abstract: FR-PO195
The Evolving Importance of mTORC2/Rictor in Autophagy Dysregulation and Diabetes-Associated Kidney Disease
Session Information
- Diabetic Kidney Disease: Basic - II
November 08, 2019 | Location: Exhibit Hall, Walter E. Washington Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Diabetic Kidney Disease
- 601 Diabetic Kidney Disease: Basic
Authors
- Alkhansa, Sahar, American University of Beirut, Beirut, Lebanon
- Ziyadeh, Fuad N., AUB, New York, New York, United States
- Eid, Assaad Antoine, American University of Beirut/Faculty of Medicine, Beirut, Lebanon
Background
Accumulating evidence suggests that autophagy plays an important role in many critical aspects of normal and disease states of the kidney including diabetic kidney disease (DKD). Podocyte integrity has been described to rely on basal autophagy. However, the exact role of autophagy in podocyte dysfunction and the mechanisms underlying diabetic-induced podocyte injury remain to be elucidated. Several signaling pathways such as mTORC1, NADPH oxidase, and the Liver-X-Receptor (LXR) pathways have been shown to orchestrate podocyte integrity in DKD. Yet, the role of mTORC2 in autophagy and its crosstalk with these key mechanistic pathways remain to be identified. For that, we investigated the role of the Nox4/LXR/mTORC2 axis on autophagy and their possible link to podocyte integrity in vitro and in animal models of type 1 and type 2 diabetes.
Methods
A conditionally immortalized human podocyte cell line was used for the in vitro studies. In parallel, type 1 diabetes was induced in mice by streptozotocin (STZ) injections and type 2 diabetes was initiated by high-fat diet followed by low-dose STZ injections. Pharmacological means were utilized to alter the expression of Nox4 (GKT), LXR (T0) and the mTORC2 (JR) signaling pathways and functional, pathological and biochemical studies were performed
Results
High glucose (HG)-induced podocyte injury is reflected by alterations in the slit diaphragm proteins and podocyte depletion accompanied by autophagy dysregulation. This was paralleled by activation of the mTORC2 pathway. HG also increased the levels of Nox4 and NADPH oxidase activity. Inhibition of mTORC2, activation of LXR, or inhibition of Nox4 decreased HG-induced ROS generation, restored autophagy homeostasis, regulated podocin levels, and reduced podocyte loss. In isolated glomeruli from the diabetic mice, there was a similar activation of the mTORC2 signaling pathway with an increase in Nox4 and NADPH oxidase activity. Inhibition of mTORC2, activation of LXR or inhibition of Nox4 restored podocin levels, reduced podocyte depletion, attenuated glomerular injury and albuminuria and regulated autophagy levels. More importantly, Chloroquine treatment, an autophagy inhibitor, mimicked the effect of HG/hyperglycemia.
Conclusion
Our data provide evidence for a novel function of mTORC2 in regulating autophagy and its role in DKD.