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Reduced expression of mitochondrial oxidative metabolism genes in skeletal muscle of women with PCOS

ABSTRACT: Recently, abnormalities in mitochondrial oxidative phosphorylation (OXPHOS) have been implicated in the pathogenesis of skeletal muscle insulin resistance in type 2 diabetes. In the present study, we hypothesized that decreased expression of OXPHOS genes could be of similar importance for insulin resistance in the polycystic ovary syndrome (PCOS). Using the HG-U133 Plus 2.0 expression array from Affymetrix, we analyzed gene expression in skeletal muscle from obese women with PCOS (n=16) and age- and body mass index-matched control women (n=13) metabolically characterized by euglycemic-hyperinsulinemic clamp and indirect calorimetry. To identify pathways of importance for the pathogenesis of insulin resistance in PCOS, we performed biological pathway analysis using Gene Set Enrichment Analysis (GSEA 1.0) and Gene Microarray Pathway Profiler (GenMAPP 2.0). The expression of 9 genes, selected according to biological relevance, was evaluated by quantitative real time PCR (q-RT-PCR). 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 (all P<0.01). GSEA and GenMAPP both revealed the same set of genes involved in OXPHOS, which was also the most downregulated biological pathway (P<0.01). These results were confirmed by q-RT-PCR of six genes from the OXPHOS gene set as well as three transcription factors known to regulate the transcription of these genes. Our results, for the first time, provide evidence for an association between insulin resistance and impaired mitochondrial oxidative metabolism in skeletal muscle in women with PCOS. This may contribute to the increased risk of type 2 diabetes observed in these women Keywords: PCOS, DNA microarray, global pathway analysis, mitochondrial oxidative metabolism, qantitative real time PCR, insulin resistance, skeletal muscle

ORGANISM(S): Homo sapiens

PROVIDER: GSE6798 | GEO | 2007/10/20

SECONDARY ACCESSION(S): PRJNA99193

REPOSITORIES: GEO

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Project description:Insulin resistance is a common metabolic abnormality in women with PCOS and leads to an elevated risk of type 2 diabetes. 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. Using Affymetrix microarrays, we examined the effect of pioglitazone (30 mg/day for 16 weeks) on gene expression in skeletal muscle of 10 obese women with PCOS metabolically characterized by a euglycemic-hyperinsulinemic clamp. Moreover, we explored gene expression changes between these PCOS patients before treatment and 13 healthy control women. Treatment with pioglitazone improved insulin-stimulated total, oxidative and non-oxidative glucose metabolism, and reduced fasting serum insulin (all p < 0.05). Global pathway analysis using Gene Map Annotator and Pathway Profiler (GenMAPP 2.1) and Gene Set Enrichment Analysis (GSEA 2.0.1) revealed a significant upregulation of genes involved in mitochondrial oxidative phosphorylation (OXPHOS), ribosomal proteins, mRNA processing reactome, translation factors, and proteasome complexes in PCOS patients after pioglitazone therapy. Quantitative real-time PCR suggested that upregulation of OXPHOS genes was mediated by an increase in PGC-1M-NM-1 expression (p < 0.05). Expression of genes involved in ribosomal proteins and OXPHOS was down-regulated in PCOS patients before treatment compared to matched healthy women using GenMAPP 2.1 and GSEA 2.1. These data indicate that pioglitazone therapy restores insulin sensitivity in part by a coordinated upregulation of genes involved in mitochondrial oxidative metabolism and protein biosynthesis in skeletal muscle of PCOS. These transcriptional effects of pioglitazone therapy may contribute to prevent the onset of type 2 diabetes in these women. Experiment Overall Design: Ten obese women of reproductive age with PCOS participated in the study to test the effect of pioglitazone therapy (data set 1). To test if pioglitazone ameliorate existing defects in PCOS patients, the expression profile of the 10 PCOS patients before treatment were compared to the same cohort of 13 control subjects (data set 2).

Project description:Insulin resistance is a common metabolic abnormality in women with PCOS and leads to an elevated risk of type 2 diabetes. 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. Using Affymetrix microarrays, we examined the effect of pioglitazone (30 mg/day for 16 weeks) on gene expression in skeletal muscle of 10 obese women with PCOS metabolically characterized by a euglycemic-hyperinsulinemic clamp. Moreover, we explored gene expression changes between these PCOS patients before treatment and 13 healthy control women. Treatment with pioglitazone improved insulin-stimulated total, oxidative and non-oxidative glucose metabolism, and reduced fasting serum insulin (all p < 0.05). Global pathway analysis using Gene Map Annotator and Pathway Profiler (GenMAPP 2.1) and Gene Set Enrichment Analysis (GSEA 2.0.1) revealed a significant upregulation of genes involved in mitochondrial oxidative phosphorylation (OXPHOS), ribosomal proteins, mRNA processing reactome, translation factors, and proteasome complexes in PCOS patients after pioglitazone therapy. Quantitative real-time PCR suggested that upregulation of OXPHOS genes was mediated by an increase in PGC-1α expression (p < 0.05). Expression of genes involved in ribosomal proteins and OXPHOS was down-regulated in PCOS patients before treatment compared to matched healthy women using GenMAPP 2.1 and GSEA 2.1. These data indicate that pioglitazone therapy restores insulin sensitivity in part by a coordinated upregulation of genes involved in mitochondrial oxidative metabolism and protein biosynthesis in skeletal muscle of PCOS. These transcriptional effects of pioglitazone therapy may contribute to prevent the onset of type 2 diabetes in these women. Keywords: PCOS, microarray, global pathway analysis, insulin resistance, pioglitazone, protein metabolism, mitochondrial oxidative metabolism

Project description:Skeletal muscle mitochondrial dysfunction is secondary to T2DM and can be improved by long-term regular exercise training Mitochondrial dysfunction has long been implicated to play a causative role in development of type 2 diabetes (T2DM). However, a growing number of recent studies provide data that mitochondrial dysfunction is a consequence of T2DM development. The aim of our study is to clarify in further detail the causal role of mitochondrial dysfunction in T2DM by a comprehensive ex vivo analysis of mitochondrial function combined with global gene expression analysis in muscle of pre-diabetic newly diagnosed untreated T2DM subjects and long-standing insulin treated T2DM subjects compared with age- and BMI-matched controls. In addition, we assessed the impact of long-term interval exercise training on physical activity performance, mitochondrial function and glycemic control in long-standing insulin-treated T2DM subjects. Ex vivo mitochondrial density, quality and functioning was comparable between pre-diabetic subjects and matched controls, however, gene expression analysis showed a switch from carbohydrate toward lipids as energy source in pre-diabetes subjects. In contrast, long-term insulin treated T2DM subjects had slightly decreased mitochondrial density and ex vivo function. Expression of Krebs cycle and OXPHOS related genes were decreased, indicating a decreased capacity to use lipids as an energy source. The insulin-treated T2DM subjects had a lower physical activity level than pre-diabetic and normoglycemic subjects. A 52 weeks exercise training of these subjects increased submaximal oxidative efficiency, increased in vivo PCr recovery rate, as well as mildly increased in vitro mitochondrial function. Gene expression of β-oxidation, Krebs cycle and OXPHOS-related genes was increased. Our data demonstrate that mitochondrial dysfunction is rather a consequence than a causative factor in T2DM development as it was only detected in overt diabetes and not in early diabetes. Regular exercise training stabilized exogenous insulin requirement and improved mitochondrial functioning, fatty acid oxidation and general physical work load capacity in long-standing insulin-treated T2DM subjects. As such, the present study shows for the first time that long-term exercise interventions are beneficial in this group of complex diabetes patient and may prevent further metabolic deterioration. Insulin-treated T2DM subjects before and after 52 weeks of exercise training (T2DM_0 and T2DM_52), normoglycemic controls (NGT) and pre-diabetes subjects (IGT) and were selected. RNA was extracted from skeletal muscle biopsies and hybridized on Affymetrix microarrays.

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Reduced expression of mitochondrial oxidative metabolism genes in skeletal muscle of women with PCOS

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