Effects of increasing glucose concentrations on gene mRNA expression in cultured rat pancreatic islets

Background and Aims, Materials and Methods: Survival and function of rat β-cells are best preserved by culture at 10 mM glucose (G10) and rapidly deteriorate at lower or higher glucose concentrations. To evaluate how glucose exerts these effects on the β-cell phenotype, we measured gene mRNA levels in rat islets precultured for 1wk in G10 and further cultured 18h in G2, G5, G10 or G30 (Affymetrix Rat Genome 230 2.0 oligonucleotide arrays, n=4). Match/mismatch probe signal intensities and differences in mRNA abundance, expressed as absolute signal log2 ratios (SLR), were calculated with GCOS software. Results: From the 31099 probe sets on the arrays, 18081 were reliably detected in at least one glucose concentration. The SLR for at least one of the comparisons between the different glucose concentrations was ≥ 1 and ≥ 0.5 in 1039 and 3530 probe sets respectively. Using Self-Organizing Map cluster analysis, 3120 of the 3530 affected probe sets were classified in 6 clusters with monophasic concentration-dependencies that differed in overall direction (increase/decrease) and glucose threshold. The remaining 410 probe sets were grouped into 5 small clusters with complex mRNA expression profiles (V-shaped or inverted V-shaped with minimum or maximum in G5 or G10). Analysis of gene function in each cluster suggested the presence of glucose co-regulated metabolic and signalling pathways (glycolysis, cholesterol synthesis, unfolded protein response…). Conclusion: These results will help identifying key molecules that maintain the differentiated β-cell phenotype as well as those responsible for β-cell deterioration after exposure to chronic hypo- or hyperglycemi