Aims Polycystic ovary syndrome (PCOS) is a common endocrine disorder in premenopausal women and is associated with insulin resistance increasing the risk for developing type 2 diabetes mellitus. Studies have shown that thiazolidinediones (TZD) improve metabolic disturbances in PCOS patients. We hypothesized that the effect of TZD in PCOS is in part mediated by changes in the transcriptional profile of muscle favoring insulin sensitivity. Methods Using the HG-U133 2.0 Plus expression array from Affymetrix, we examined the effect of pioglitazone (30 mg/day for 16 weeks) on gene expression in skeletal muscle of 10 obese women with PCOS (dataset 1). Furthermore, evaluation of gene expression changes between PCOS patients before treatment and control subjects were performed (dataset 2). All subjects were metabolically characterised by a euglycemic-hyperinsulinemic clamp combined with indirect calorimetry. Constant normalization of arrays and gene expression index calculation were done using the R statistical software. We performed global pathway analysis to identify significant pathways in the two datasets using Gene Set Enrichment Analysis (GSEA 2.0) and Gene Microarray Pathway Profiler (GenMAPP 2.1). The expression of 9 genes (dataset 1), selected according to biological relevance, was evaluated by quantitative real time PCR (q-RT-PCR) employing TaqMan gene expression assays. Results Treatment with pioglitazone improved total, oxidative and non-oxidative glucose metabolism, and reduced fasting serum insulin (Table 1). Before treatment, women with PCOS were characterized by fasting hyperinsulinemia and impaired insulin-stimulated glucose disposal - caused by reduced glucose oxidation and storage - as well as impaired suppression of lipid oxidation (Table 2). Evaluating the results from data set 1, pathways representing OXPHOS genes were the two most upregulated gene sets and ribosomal proteins were the fourth most upregulated gene set in GSEA (Table 3). In GenMAPP, these pathways were the two most upregulated gene sets (Table 4). In data set 2, pathways representing OXPHOS genes were the most downregulated gene sets in GSEA (Table 5), and the second most downregulated gene set after ribosomal proteins in GenMAPP (data not shown). Results from dataset 1 were confirmed by q-RT-PCR showing upregulation of two of six genes from the OXPHOS gene set as well as one of three transcription factors known to regulate the transcription of these genes. Moreover, one gene from the OXPHOS gene set was marginally significant (P=0.057) (Figure 2). Conclusions These data indicate that pioglitazone therapy restores insulin sensitivity in part by a coordinated upregulation of genes involved in mitochondrial oxidative metabolism in skeletal muscle in PCOS.
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Xth International Symposium on Insulin Receptors and Insulin Action, 2007