294-LB: Transcriptome-Wide Signals Converge Upon Mitochondrial Function in Developmental Stages of Type 2 Diabetes in Human Skeletal Muscle

Skeletal muscle is a major contributor to overall glucose homeostasis in the body and together with the liver is chiefly responsible for the whole-body insulin sensitivity. However, few studies have investigated the transcriptional signature of insulin resistance in skeletal muscles, at different stages of T2D development. Thus, the aim of this study was to identify the transcriptional signature of dysregulated glucose metabolism in skeletal muscle in humans by profiling the transcriptome with next-generation sequencing (NGS). We selected 40 sedentary males, aged 40-65 years, with BMI 26-33 kg/m2, diagnosed into three groups: 18 normoglycemics, 14 prediabetics and 8 subjects with type 2 diabetes. mRNA was extracted from biopsied Vastus lateralis muscles and sequenced with Illumina HiSeq 4000.Comparing normoglycemic and diabetic subjects revealed 4404 significantly differentially expressed (DE) genes, which represents around 30% of all mapped genes in studied samples. For the comparison between type 2 diabetics and prediabetics, the number of DE genes was 4055 genes. Interestingly we found no significantly DE genes between normoglycemics and prediabetics. KEGG enrichment analysis revealed that DE pathways between diabetics vs. nondiabetics were enriched for pathways related to oxidative phosphorylation, thermogenesis, nonalcoholic fatty liver disease and neurological diseases, which share the same underlying mechanism: mitochondrial dysfunction.These results indicate that skeletal muscle contributes most to overt T2D, with a possible indication that the liver contributes most to early stages the disease development. Differences observed between type 2 diabetics and the two remaining groups, occurring primarily in oxidative phosphorylation and electron transport chain pathways suggests that mitochondrial dysfunction plays the predominant role in the pathogenesis of T2D.