Mitochondria functionality and sperm quality

Abstract

Although mitochondria are best known for being the eukaryotic cell powerhouses, these organelles participate in various cellular functions besides ATP production, such as calcium homoeostasis, generation of reactive oxygen species (ROS), the intrinsic apoptotic pathway and steroid hormone biosynthesis. The aim of this review was to discuss the putative roles of mitochondria in mammalian sperm function and how they may relate to sperm quality and fertilisation ability, particularly in humans. Although paternal mitochondria are degraded inside the zygote, sperm mitochondrial functionality seems to be critical for fertilisation. Indeed, changes in mitochondrial integrity/functionality, namely defects in mitochondrial ultrastructure or in the mitochondrial genome, transcriptome or proteome, as well as low mitochondrial membrane potential or altered oxygen consumption, have been correlated with loss of sperm function (particularly with decreased motility). Results from genetically engineered mouse models also confirmed this trend. On the other hand, increasing evidence suggests that mitochondria derived ATP is not crucial for sperm motility and that glycolysis may be the main ATP supplier for this particular aspect of sperm function. However, there are contradictory data in the literature regarding sperm bioenergetics. The relevance of sperm mitochondria may thus be associated with their role in other physiological features, particularly with the production of ROS, which in controlled levels are needed for proper sperm function. Sperm mitochondria may also serve as intracellular Ca 2C stores, although their role in signalling is still unclear.

Effect of oleic-linoleic acid and ?-sitosterol to freezing extender of bulls and stallions semen

“…This staining is used to evaluate the ability of the mitochondria to produce ATP, which sustains the activity of spermatozoa and is thus positively correlated both with cellular motility and viability (GARNER et al, 1997). In addition, mitochondrial activity is related to Ca 2+ homeostasis and to the production of reactive oxygen species (ROS) that, at controlled levels, are part of the physiological events associated with fertilization (AMARAL et al, 2013). In the present study, the addition of lipids had no effect on mitochondrial activity in bovines or in equines.…”

Physiological and Pathological Roles of Free Radicals in Male Reproduction

“…Likewise, peroxides have been associated with formation of the mitochondrial capsulea coat surrounding sperm mitochondria providing protection against possible proteolytic degradation [54]. It is suggested that during spermatogenesis peroxides may oxidize the active form of phospholipid hydroperoxide glutathione peroxidase (PHGPx), creating an intermediate that subsequently interacts with thiol groups to form a seleno-disulfide bond.…”

“…Mitochondria require such protection as their proper function is crucial for metabolism, cell cycle control and oxidative balance [51,53,54].…”

“…More importantly, a direct relationship has been reported between male fertility and phospholipid hydroperoxide glutathione peroxidase (PHGPx; GPx4), a selenoprotein that is highly expressed in testicular tissue and has a prominent role in the formation of the mitochondrial capsule [51,53,54]. Glutathione peroxidases remove peroxyl (ROO • ) radicals from various peroxides, including hydrogen peroxide [13].…”

“…• Cofactor of phospholipid hydroxyperoxide glutathione peroxidase, important for chromatin condensation and formation of the mitochondrial capsule [52][53][54] Albumin • A highly soluble protein containing 585 amino acids • A key element in the regulation of osmotic pressure and distribution of fluid between different compartments [143] and able to bind metals ions, fatty acids, drugs and hormones.…”