In women, hormonal ageing, termed menopause, is associated with decrements in skeletal muscle mass and function.
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One possible route through which estrogens may affect skeletal muscle mass is apoptosis coordinating microRNAs.
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We studied the effect of estradiol deficiency on the expression of apoptosis pathway associated microRNAs and their targets in skeletal muscle in a mouse model mimicking menopause.
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Estradiol deficiency downregulated several microRNAs related to apoptosis and may represent a mechanism that results in reduced muscle mass.
Abstract
Background
Menopause leads to estradiol (E2) deficiency that is associated with decreases in muscle mass and strength. Here we studied the effect of E2 deficiency on microRNA (miR) signaling that targets apoptotic pathways.
Methods
C57BL6 mice were divided into control (normal estrous cycle, n = 8), OVX (E2 deficiency, n = 7) and OVX + E2 groups (E2-pellet, n = 4). Six weeks following the OVX surgery, mice were sacrificed and RNA isolated from gastrocnemius muscles. miR-profiles were studied with Next-Generation Sequencing (NGS) and candidate miRs verified using qPCR. The target proteins of the miRs were found using in silico analysis and measured at mRNA (qPCR) and protein levels (Western blot).
Results
Of the apoptosis-linked miRs present, eleven (miRs-92a-3p, 122-5p, 133a-3p, 214-3p, 337-3p, 381-3p, 483-3p, 483-5p, 491-5p, 501-5p and 652-3p) indicated differential expression between OVX and OVX + E2 mice in NGS analysis. In qPCR verification, muscle from OVX mice had lower expression of all eleven miRs compared with OVX + E2 (p < 0.050). Accordingly, OVX had higher expression of cytochrome C and caspases 6 and 9 compared with OVX + E2 at the mRNA level (p < 0.050). At the protein level, OVX also had lower anti-apoptotic BCL-W and greater pro-apoptotic cytochrome C and active caspase 9 compared with OVX + E2 (p < 0.050).
Conclusion
E2 deficiency downregulated several miRs related to apoptotic pathways thus releasing their targets from miR-mediated suppression, which may lead to increased apoptosis and contribute to reduced skeletal muscle mass.