Abstract
miR-26a is associated with sperm metabolism and can affect sperm motility and apoptosis. However, how miR-26a affects sperm motility remains largely unknown. Our previous study indicated that the PDHX gene is predicted to be a potential target of miR-26a, which is responsible for pyruvate oxidative decarboxylation which is considered as a key step for connecting glycolysis with oxidative phosphorylation. In this study, we first reported a potential relationship between miR-26a and PDHX and their expressions in fresh, frozen-thawed, and epididymal boar sperm. Then, sperm viability and survival were determined after transfection of miR-26a. mRNA and protein expression level of PDHX in the liquid-preserved boar sperm after transfection were also determined by RT-qPCR and Western Blot (WB). Our results showed that expression level of PDHX was significantly increased during sperm transit from epididymal caput to corpus and cauda. Similarly, expression of PDHX was significantly higher (P < 0.05) in fresh sperm as compared to epididymal cauda and frozen-thawed sperm. However, the expression of miR-26a in epididymal corpus sperm was significantly higher (P < 0.05) than that of caput and cauda sperm. Furthermore, after transfection of boar sperm with miR-26a mimic and inhibitor under liquid storage, the lowest and highest sperm viability was observed in miR-26a mimic and inhibitor treatment (P < 0.05), respectively. The protein levels of PDHX, after 24 and 48 h of transfection of miR-26a mimics and inhibitor, were notably decreased and increased (P < 0.05), respectively, as compared to negative control (NC) group. In conclusion, the novel and enticing findings of our study provide a reasonable evidence that miR-26a via PDHX, a link between glycolysis and oxidative phosphorylation, could regulate the glycometabolic pathway which eventually affect boar sperm viability and survival.
Highlights
Following spermatogenesis in testes, sperm undergo distinct post-gonadal phases of differentiation and maturation while transiting in the epididymis and subsequently attain maturity and progressive motility [1,2]
It has been reported that the expression level of miR-26a in highly motile frozen-thawed sperm was significantly higher as compared to the low-motile frozen-thawed sperm [49]. These results provide reasonable evidence that miR-26a may be involved in regulating the sperm metabolism and apoptosis, and in turn can affect sperm motility and survival
The prediction results showed that pyruvate dehydrogenase complex component X (PDHX) 30 -UTR harbors only one potential target site for these findings provide reasonable evidence that PDHX is a direct target gene of miR-26a miRNA-26a based on TargetScan, miRWalk, miRanda, and picTar
Summary
Sperm undergo distinct post-gonadal phases of differentiation and maturation while transiting in the epididymis and subsequently attain maturity and progressive motility [1,2]. It has been suggested that under liquid storage conditions sperm exhibit morphological and functional changes similar to natural aging process along with apoptotic-like changes [3,4]. The metabolic activity of frozen-thawed sperm is inhibited, which contributes to the decreased sperm motility [8]. Sperm metabolism is an essential process by which sperm obtain energy via utilizing the substances dissolved in seminal plasma and cytosol. It plays an important role in maintaining normal function of sperm such as motility, survival and fertility [9,10]. The metabolic activity of sperm is crucial for sustaining its survival and movement. Due to the lower endogenous sugar content, sperm rely mainly on the exogenous sugar sources to fulfill energy requirements [11,12]
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