Endocrine Abstracts

Polycystic ovary syndrome (PCOS) is an endocrine and metabolic disorder affecting women of reproductive age. The main features of PCOS are hyperandrogenism and reproductive and metabolic dysfunctions. We have previously shown that muscle contractions induced by either electrical stimulations or exercise act through partially similar signaling pathways in the muscle to induce glucose uptake in the acute response. Long-term electrical stimulations decrease circulating testosterone, HOMA-IR, and HbA1c in overweight/obese women with PCOS, but the mechanism is largely unknown. Here, we used transcriptomic and proteomic analyses to provide new mechanistic explanations to the improved glucose homeostasis in response to 30 min of electrical stimulations, 3 times/week for 5 weeks. Skeletal muscle biopsies from 10 women with PCOS were subjected to global methylation, transcriptomics and proteomic analysis at baseline and after 5 weeks of treatment. Changes in protein expression between baseline and after treatment were based on Student’s t-test (P<0.05) and a fold change >50%. Changes in skeletal muscle DNA methylation and gene expression in response to electrical stimulation were based on linear regression analysis (P< 0.01) and a fold change >20%. 12 unique transcripts exhibited increased expression in skeletal muscle after 5 weeks of treatment. Four types of collagens were upregulated, and together with VCAN and LUM, these genes were confirmed by gene ontology analysis to play a role in extracellular matrix organization and skeletal system development. Next, we analyzed if the response to electrical stimulation involved DNA methylation changes in skeletal muscle. The absolute changes in methylation were small and ranged from −1.29% to +0.72% points. The vast majority of the 43 significant CpG sites (75%) displayed decreased DNA methylation in response to electrical stimulation. Since relatively few genes and methylation sites were regulated in response to repeated electrical stimulations, we investigated if the long-term effects were regulated at the protein level. More than 300 proteins changed expression after treatment. 97% of these were upregulated and enriched pathways involved exocytosis, extracellular matrix organisation, integrin-mediated signalling, transforming growth factor production, and protein metabolic processes. Collagen 1A1 and 1A2 were upregulated both at the gene and protein expression level after electrical stimulation. One can speculate that up-regulation of integrins, collagens, and transforming growth factor-beta-1 likely lead to ECM remodeling, which can provide protective adaptation to repeated stimulation, and improved muscle strength and function. In conclusion, changes at the protein level mediate the response to long-term electrically stimulated muscle contractions.