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Kidney Week

Abstract: FR-PO198

The Insulin/Insulin-Like Growth Factor Axis Is Critical for Podocyte Function but Partial Inhibition of IGF1 Signalling Is Physiologically Beneficial

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Hurcombe, Jenny, University of Bristol, Bristol, United Kingdom
  • Marchetti, Micol, Uppsala University, Uppsala, Sweden
  • Barrington, Fern, University of Bristol, Bristol, United Kingdom
  • Ni, Lan, University of Bristol, Bristol, United Kingdom
  • Lay, Abigail Charlotte, University of Bristol, Bristol, United Kingdom
  • Brinkkoetter, Paul T., University Hospital Cologne, Cologne, Germany
  • Holzenberger, Martin, INSERM, Paris, France
  • Welsh, Gavin Iain, University of Bristol, Bristol, United Kingdom
  • Coward, Richard, University of Bristol, Bristol, United Kingdom
Background

Abnormalities in insulin signalling through the insulin receptor (IR) have previously been found to be critical for podocyte function and this study aims to define the physiological importance of the related insulin-like growth factor 1 receptor (IGF1R) and combined IR/IGF1R in podocytes.

Methods

The Cre-loxP system was used to generate mice with podocyte-specific IGF1R and simultaneous IR/IGF1R gene inactivation. In vitro models of receptor knockdown were engineered by applying extrinsic lentiviral Cre recombinase to podocytes derived from IR, IGF1R and IR/IGF1R floxed mice.

Results

We initially generated podocyte IGF1R knockout (podIGF1RKD) mice by crossing IGF1R floxed with mice expressing conventional Cre recombinase under the control of a podocin promotor. Despite 80% knockdown of the IGF1R in this model, podIGF1RKD mice exhibited no changes in renal histology or urinary albumin:creatinine (uACR) at 9 months when compared with littermate controls. However, when these mice were stressed with Adriamycin we, surprisingly, found that podIGF1RKD mice were protected against disease progression with uACR 50% lower than IGF1R sufficient controls.
To increase the efficiency of knockout and understand if there was compensation within the IR/IGF1R axis we also generated two additional models using a new podocyte specific Cre driver that is not subject to epigenetic degradation (podIGF1RKO and podIR/IGF1R DKO mice). podIGF1RKO mice were albuminuric at 24 weeks while podIR/IGF1R DKO mice developed a severe kidney phenotype with global sclerosis, renal failure and death between 4 and 24 weeks.
>95% loss of IGF1R in cultured podocytes augmented AKT and ERK activation in response to insulin but resulted in ~50% cell death after 7 days. To identify further differentially regulated signalling pathways, IR, IGF1R and IR/IGF1R knockout cells were subjected to TMT phosphoproteomic analysis in the basal state and when acutely stimulated with insulin or IGF1.

Conclusion

Collectively this work reveals the critical importance of podocyte IGF/insulin signalling and that only a fraction of receptor activity is required to maintain function. We also show that partial inactivation of podocyte IGF1R is beneficial in some disease settings.