Reactive oxygen species

Fructose is now such an important component of human diets that increasing attention is being focused on the fructose transporter GLUT5. In this review, we describe the regulation of GLUT5 not only in the intestine and testis, where it was first discovered, but also in the kidney, skeletal muscle, fat tissue, and brain where increasing numbers of cell types have been found to have GLUT5. GLUT5 expression levels and fructose uptake rates are also significantly affected by diabetes, hypertension, obesity, and inflammation and seem to be induced during carcinogenesis, particularly in the mammary glands. We end by highlighting research areas that should yield information needed to better understand the role of GLUT5 during normal development, metabolic disturbances, and cancer.

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Regulation of the fructose transporter GLUT5 in health and disease.

Mammalian sperm cells are activated prior to fertilization by high bicarbonate levels, which facilitate lipoprotein-mediated cholesterol efflux. The role of bicarbonate and cholesterol acceptors on the cholesterol organization in the sperm plasma membrane was tested. Bicarbonate induced an albumin-independent change in lipid architecture that was detectable by an increase in merocyanine staining (due to protein kinase A-mediated phospholipid scrambling). The response was limited to a subpopulation of viable sperm cells that were sorted from the non-responding subpopulation by flow cytometry. The responding cells had reduced cholesterol levels (30% reduction) compared with non-responding cells. The subpopulation differences were caused by variable efficiencies in epididymal maturation as judged by cell morphology. Membrane cholesterol organization was observed with filipin, which labeled the entire sperm surface of non-stimulated and non-responding cells, but labeled only the apical surface area of bicarbonate-responding cells. Addition of albumin caused cholesterol efflux, but only in bicarbonate-responding cells that exhibited virtually no filipin labeling in the sperm head area. Albumin had no effect on other lipid components, and no affinity for cholesterol in the absence of bicarbonate. Therefore, bicarbonate induces first a lateral redistribution in the low cholesterol containing spermatozoa, which in turn facilitates cholesterol extraction by albumin. A model is proposed in which phospholipid scrambling induces the formation of an apical membrane raft in the sperm head surface that enables albumin mediated efflux of cholesterol.

Bicarbonate stimulated phospholipid scrambling induces cholesterol redistribution and enables cholesterol depletion in the sperm plasma membrane

Sperm cryopreservation update: Cryodamage, markers, and factors affecting the sperm freezability in pigs.

The cryopreservation of spermatozoa was introduced in the 1960s as a route to fertility preservation. Despite the extensive progress that has been made in this field, the biological and biochemical mechanisms involved in cryopreservation have not been thoroughly elucidated to date. Various factors during the freezing process, including sudden temperature changes, ice formation and osmotic stress, have been proposed as reasons for poor sperm quality post-thaw. Little is known regarding the new aspects of sperm cryobiology, such as epigenetic and proteomic modulation of sperm and trans-generational effects of sperm freezing. This article reviews recent reports on molecular and cellular modifications of spermatozoa during cryopreservation in order to collate the existing understanding in this field. The aim is to discuss current freezing techniques and novel strategies that have been developed for sperm protection against cryo-damage, as well as evaluating the probable effects of sperm freezing on offspring health.

Sperm cryopreservation: A review on current molecular cryobiology and advanced approaches.

Freezability prediction of boar ejaculates assessed by functional sperm parameters and sperm proteins.

Semen quality of postpubertal boars during increasing and decreasing natural photoperiods

Artificial insemination with frozen-thawed semen in pigs is not a routine technique; its use is restricted to specific cases, such as preservation of valuable genetic material (germplasm banks), safety strategies in case of natural disasters, long-distance transport of sperm, and in combination with sex-sorting. Cryoinjuries resulting from freeze-thawing protocols are a major concern with regard to the fertilization capacity of the treated sperm, which is lower than that of liquid-stored semen. Here, we provide an overview of artificial insemination using cryopreserved sperm, and summarize the factors that influence cryopreservation success before, during, and after freeze-thaw (i.e., sperm selection before starting the cryopreservation process, holding time, use of cryoprotectants, and rates of freezing and thawing) and that are driving the identification of biomarkers to predict sensitivity to cryodamage. Three different artificial insemination techniques (conventional or intracervical; intrauterine; and deep intrauterine) are also discussed with regards to their relevance when using frozen-thawed semen. Finally, we review the use of additives to freezing and thawing media, given reports that they may maintain and improve the quality and fertilizing capacity of frozen-thawed sperm. In sum, artificial insemination with frozen-thawed boar sperm can provide reasonable fertility outcomes, if freezable ejaculates, specific additives, and appropriate insemination techniques are used.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/mrd.22840

Artificial insemination with frozen‐thawed boar sperm

Acrosin-binding protein (ACRBP) and triosephosphate isomerase (TPI) are good markers to predict boar sperm freezing capacity

Summary

The main aim of this work was to evaluate how supplementing freezing media with reduced glutathione (GSH) affected the ‘in vivo’ fertilizing ability of boar semen subjected to cryopreservation procedures. With this purpose, 12 ejaculates coming from 12 boars were cryopreserved in the presence or absence of 2 mm GSH, whereas the same number of extended ejaculates coming from the same boars was used as negative/farm controls. Eight different sperm parameters (levels of free-cysteine residues in sperm nucleoproteins, DNA fragmentation, sperm viability, acrosome-membrane integrity, intracellular peroxide and superoxide levels, and total and progressive sperm motility) were evaluated before freezing and after 30 and 240 min of thawing. In addition, a total of 180 multiparous sows were used in the field fertility trials, the females being randomly divided into three groups and inseminated with extended, frozen-thawed control or frozen-thawed semen supplemented with 2 mm GSH. The presence of GSH in the freezing media significantly (p < 0.05) increased farrowing rates and the number of total born piglets and alive born piglets, and partially counteracted the cryopreservation-induced damages inflicted on frozen-thawed spermatozoa. We can thus conclude that supplementing freezing media with 2 mm GSH greatly improves boar sperm cryopreservation technology, as it significantly improves the fertilizing ability of frozen-thawed spermatozoa.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.2047-2927.2013.00144.x

S. Bonet

Papers

Freezability prediction of boar ejaculates assessed by functional sperm parameters and sperm proteins.

Semen quality of postpubertal boars during increasing and decreasing natural photoperiods

Artificial insemination with frozen‐thawed boar sperm

Acrosin-binding protein (ACRBP) and triosephosphate isomerase (TPI) are good markers to predict boar sperm freezing capacity

Supplementing cryopreservation media with reduced glutathione increases fertility and prolificacy of sows inseminated with frozen-thawed boar semen.