MICROARRAY ANALYSIS OF TYPE 2 DIABETIC ISOLATED HUMAN ISLETS

Introduction: Type 2 diabetes (T2D) is a multifactorial syndrome with beta-cell failure playing a major role. However, information on islet transcriptome in human T2D is scanty. Objectives: To better understand the pattern of the alterations in the diabetic condition, we performed microarray analysis on T2D islet samples. Materials and Methods: The analysis, followed by quantitative RT-PCR (qPCR) of selected genes, was performed on six T2D (age: 71±9yrs; gender: 3M/3F; BMI: 26.0±2.2Kg/m2) and 7 nondiabetic (ND, age:58±17yrs; gender: 4M/3F; BMI: 24.8±2.5Kg/m2) islet preparations. RNA was hybridized on Affymetrix chips (HG U133A). Gene expression intensities were normalized with RMA and differential expression was assessed using the limma. Results: When T2D islets were compared with ND samples, the expression of 1345 probe sets resulted significantly (p 2.0) different; of these, 59 were upregulated and 1286 downregulated. By Gene Ontology and KEGG analysis it was observed that the differently expressed genes influenced 21 processes and 13 pathways. Such findings were confirmed by the Gene Set Enrichment Analysis, performed to evaluate how the overall gene expression profile could influence intracellular processes. This analysis showed that out of 1419 gene sets studied, 195 were positively and 42 negatively enriched inT2D islets. The expression of genes involved in oxidative phosphorylation and citrate cycle resulted consistently changed in T2D samples; when qPCR analysis was performed, a significant reduction in the expression of pyruvate and succinate dehydrogenase complexes was found. Conclusion: In conclusion, T2D islets show many alterations of transcriptome, including changes of genes involved in mitochondrial ATP production