Diabetologie und Stoffwechsel 2012; 7 - P_18
DOI: 10.1055/s-0032-1314515

Effects of Insulin Degrading Enzyme (IDE)-activity on the liver cancer cell transcriptome

O Pivovarova 1, 2, I Ilkavets 3, S Zhuk 4, A Malashicheva 4, A Kostareva 4, S Dooley 3, AFH Pfeiffer 1, 2, N Rudovich 1, 2
  • 1German Institute of Human Nutrition Potsdam-Rehbruecke, Department of Clinical Nutrition, Nuthetal, Germany
  • 2Charité University Medicine, Campus Benjamin Franklin, Department of Endocrinology, Diabetes and Nutrition, Berlin, Germany
  • 3Medical Clinic II, Faculty of Medicine Mannheim at Heidelberg University, Molecular Hepatology – Alcohol Associated Diseases, Mannheim, Germany
  • 4Almazov Federal Heart, Blood and Endocrinology Center, Institute of Molecular Biology and Genetics, Saint-Petersburg, Russian Federation

Aims: Type 2 diabetes mellitus (T2DM) characterized by hyperinsulinemia is an independent risk factor for development and progression of hepatocellular carcinoma. Insulin degrading enzyme (IDE) is a major enzyme responsible for insulin degradation. We and others demonstrated that metabolic modulation of IDE activity is more important for its overall action than alterations of its protein level. Inhibition of IDE activity results in increased intracellular insulin concentration, which is probably crucial for insulin-dependent regulation of gene expression and cell proliferation. Therefore, modulating IDE activity may represent a key link between T2DM and liver cancer. Here, we characterized variations in the gene expression of HepG2 hepatoma cell line upon modulation of IDE activity.

Methods: We analyzed the HepG2 cell transcriptome under four conditions: in untreated cells or after insulin treatment (10 nM insulin for 24h) with or without inhibition of IDE activity. To modulate IDE activity in HepG2 cells, known IDE inhibitors (bacitracin, N-ethylmaleimide, 1,10-phenanthroline) or IDE silencing (RNAi) were used. Full human genome Affymetrix microarrays (19,741 transcripts) were used for gene expression profiling.

Results: All used chemicals demonstrated toxicity for HepG2 cells in concentrations, which are effective to inhibit IDE activity according to literature data. Therefore, only IDE RNAi was used in experiments for transcriptome analyses. The IDE modulation regulated a greater part of transcriptome in comparison with insulin effects (0.05% vs. 0.71% with -log10(p)=-2.6, respectively). In basal state, IDE silencing led to the regulation of genes related to MAPK and p53 signaling pathways as well as endocytosis and ligand-receptor interactions. Insulin treatment in IDE knockdown cells resulted in expression alterations of cell cycle genes that were not detected in control cells. Moreover, proliferation markers MKI67, MCM2 and PCNA were significantly upregulated upon RNAi for IDE.

Conclusions: Inhibition of IDE activity can lead to insulin mediated upregulation of proliferation pathway genes in liver cells. Thus, IDE becomes a potential target for therapeutic intervention in T2DM and cancer.

The study was supported by a grant of German Diabetic Association (allgemeine Projektförderung der DDG 2011).