Menopausal transition alters female skeletal muscle transcriptome

Objectives Although skeletal muscle is a target of hormonal regulation, the muscle transcriptome, including messenger-RNA (mRNA), long non-coding RNAs (lncRNAs), and microRNAs (miRNAs) has not previously been studied across the menopausal transition. Thus, we took a multi-RNA-omics approach to get insight into transcriptome-wide events of menopause. Methods We included baseline and follow-up muscle samples from seven early (EarlyMT) and 17 late perimenopausal (LateMT) women transitioning to early postmenopause during the study. Total RNA was sequenced and differential expression (DE) of the transcriptome was investigated. Gene functions were investigated with pathway analyses and protein level expression with Western Blot. Results We found 30 DE mRNA genes in EarlyMT and 19 in LateMT participating in pathways controlling cell death, growth, and interactions with the external environment. Lack of protein level changes may indicate a specific role of the regulatory RNAs during menopause. 10 DE lncRNA transcripts but no DE lncRNA genes were identified. No DE miRNAs were found. We identified putative regulatory networks likely to be affected by estradiol availability. Changes in gene expression were correlated with changes in body composition variables, indicating that muscularity and adiposity regulators are affected by menopausal transition. We also found correlations between gene expression and physical activity levels. Conclusions The observed DE genes and their regulatory networks offer novel mechanistic insights into factors affecting body composition during and after menopause. Our results imply that physiological deteriorations orchestrated by the muscle transcriptome likely depend on the magnitude of hormonal change and are influenced by physical activity

Interaction of the C2C12 myotube contractions and glucose availability on transcriptome and extracellular vesicle microRNAs

Exercise-like electrical pulse stimulation (EL-EPS) of myotubes mimics many key physiological changes induced by in vivo exercise. Besides enabling intracellular research, EL-EPS allows to study secreted factors, including muscle-specific microRNAs (myomiRs) carried in extracellular vesicles (EVs). These factors can participate in contraction-induced intercellular crosstalk and may mediate health benefits of exercise. However, the current knowledge of these responses, especially under variable nutritional conditions, is limited. We investigated the effects of EL-EPS on C2C12 myotube transcriptome in high and low glucose conditions by messenger RNA sequencing, while the expression of EV-carried miRNAs was analyzed by small RNA sequencing and RT-qPCR. We show that higher glucose availability augmented contraction-induced transcriptional changes and that the majority of the differentially expressed genes were upregulated. Furthermore, based on the pathway analyses, processes related to contractility and cytokine/inflammatory responses were upregulated. Additionally, we report that EL-EPS increased packing of miR-1-3p into EVs independent of glucose availability. Together our findings suggest that in vitro EL-EPS is a usable tool not only to study contraction-induced intracellular mechanisms, but also extracellular responses. The distinct transcriptional changes observed under variable nutritional conditions emphasize the importance of careful consideration of media composition in future exercise-mimicking studies.peerReviewe

Extracellular vesicles and high‐density lipoproteins : Exercise and oestrogen‐responsive small RNA carriers

Decreased systemic oestrogen levels (i.e., menopause) affect metabolic health. However, the detailed mechanisms underlying this process remain unclear. Both oestrogens and exercise have been shown to improve metabolic health, which may be partly mediated by circulating microRNA (c-miR) signalling. In recent years, extracellular vesicles (EV) have increased interest in the field of tissue crosstalk. However, in many studies on EV-carried miRs, the co-isolation of high-density lipoprotein (HDL) particles with EVs has not been considered, potentially affecting the results. Here, we demonstrate that EV and HDL particles have distinct small RNA (sRNA) content, including both host and nonhost sRNAs. Exercise caused an acute increase in relative miR abundancy in EVs, whereas in HDL particles, it caused an increase in transfer RNA-derived sRNA. Furthermore, we demonstrate that oestrogen-based hormonal therapy (HT) allows the acute exercise-induced miR-response to occur in both EV and HDL particles in postmenopausal women, while the response was absent in nonusers.peerReviewe

Systemic circulating microRNA landscape in Lynch syndrome

Circulating microRNAs (c-miRs) are small non-coding RNA molecules that migrate throughout the body and regulate gene expression. Global c-miR expression patterns (c-miRnomes) change with sporadic carcinogenesis and have predictive potential in early detection of cancers. However, there are no studies that have assessed whether c-miRnomes display similar potential in carriers of inherited pathogenic mismatch-repair gene variants (path_MMR), known as Lynch syndrome (LS), who are predisposed to highly increased cancer risk. Using high-throughput sequencing and bioinformatic approaches, we conducted an exploratory analysis to characterize systemic c-miRnomes of path_MMR carriers, sporadic rectal cancer patients and non-LS controls. We showed for the first time that cancer-free path_MMR carriers have a systemic c-miRnome of 40 differentially expressed c-miRs that can distinguish them from non-LS controls. The systemic c-miRnome of cancer-free path_MMR carriers also resembles the systemic c-miRnomes of cancer patients with or without path_MMR. Our pathway analysis linked the found differentially expressed c-miRs to carcinogenesis. A total of 508 putative target genes were identified for 32 out of 40 differentially expressed c-miRs, and 238 of them were enriched in cancer-related pathways. The most enriched c-miR-target genes include well-known oncogenes and tumor suppressor genes such as BCL2, AKT3, PIK3CA, KRAS, NRAS, CDKN1A and PIK3R1. Taken together, our findings suggest that LS and sporadic carcinogenesis share common biological pathways and alterations in these pathways can produce a c-miR signature which can track potential oncogenic stress in cancer-free path_MMR carriers. Therefore, c-miRs hold potential in monitoring the LS risk stratification patterns during clinical surveillance or cancer management.peerReviewe