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Abstract: TH-PO880

MicroRNA-155 Upregulation Induces Podocyte Insulin Resistance: A New Therapeutic Target in Diabetic Nephropathy?

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Wonnacott, Alexa, Cardiff University, Cardiff, United Kingdom
  • Lay, Abigail Charlotte, University of Bristol, Bristol, United Kingdom
  • Barrington, Fern, University of Bristol, Bristol, United Kingdom
  • Bowen, Timothy, Cardiff University, Cardiff, United Kingdom
  • Coward, Richard, University of Bristol, Bristol, United Kingdom
  • Fraser, Donald, Cardiff University, Cardiff, United Kingdom
Background

Loss of podocyte-specific insulin-sensitivity results in histological features of diabetic nephropathy (DN) in mice, implicating this pathway in disease development. MicroRNAs (miRNAs) regulate expression of most mammalian protein coding genes at the post-transcriptional level, and are critical regulators of insulin responses in “traditionally” insulin-sensitive tissues, liver, fat and muscle. The role of miRNAs in podocyte insulin-signalling is unknown. We hypothesise that miRNA-driven loss of podocyte insulin responses triggers DN development.

Methods

Podocytes were rendered insulin-resistant by culture in diabetogenic media containing high dose insulin, glucose and inflammatory cytokines. Microarray analysis was performed to compare miRNA expression profiles of wild type and insulin-resistant podocytes, and differential expression of selected miRNAs was validated by RT-qPCR. In vitro manipulation of differentially expressed miRNAs was achieved using miRvana mimics and inhibitors, and insulin responses assessed by Western Blot and tritiated glucose uptake assay.

Results

Differential expression of 103 miRNAs was detected. Five miRNAs were selected for further study based on expression fold change, a statistical significance threshold of p<0.0002 and bioinformatic evidence of targets in insulin-signalling pathways. MiR-155,-146a,-222 and -204 were validated by RT-qPCR. MiR-155 overexpression in podocytes repressed expression of target mRNA PI3KR1, reducing subsequent Akt phosphorylation. Furthermore, Insulin-stimulated glucose uptake was reduced in miR-155 over-expressing podocytes.

Conclusion

MicroRNA-155 is upregulated in podocyte insulin-resistance in vitro. Insulin-resistance may be effected via PI3KR1 repression, leading to reduced insulin-signalling via the PI3K/Akt pathway and impaired downstream glucose uptake. Thus miR-155 may be therapeutically manipulated as a novel podocyte insulin-sensitiser to halt the progression of DN.