Low-Fat, High-Carbohydrate Diets Reduce Body Weight and Sperm Count but Increase Sperm Motility in Mice.

BACKGROUND: Male reproduction is impacted by both over- and under-nutrition, demonstrated by animal studies using high-fat and low-protein dietary interventions. Little is known about the impacts of low-fat, high-carb diets and types of dietary carbohydrates on sperm traits. OBJECTIVES: Using a nutritional geometry approach, we investigated the effects of partially or completely substituting glucose for fructose in isocaloric diets containing either 10%, 20%, or 30% fat (by energy) on sperm traits in mice. METHODS: Male C57BL/6J mice were fed 1 of 15 experimental diets for 18 wk starting from 8 wk of age. Reproductive organs were then harvested, and sperm concentration, motility, and velocity were measured using Computer-Assisted Sperm Analysis. RESULTS: Increasing dietary fat from 10% to 30% while maintaining energy density at 14.3 kJ/g and protein content at 20% resulted in increased body weight and sperm production but reduced the percentage of motile sperm. Body weight and seminal vesicle weight were maximized on diets containing a 50:50 mix of fructose and glucose, but carbohydrate type had few significant impacts on epididymal sperm traits. CONCLUSIONS: The opposing impacts of dietary fat on mouse sperm quantity and quality observed suggest that male fertility may not be optimized by a single diet; rather, context-specific dietary guidelines targeted to specific concerns in semen quality may prove useful in treating male infertility.

Molecular insights to the sperm-cervix interaction and the consequences for cryopreserved sperm.

Cryopreserved ram spermatozoa are limited in their capacity to traverse the ovine cervix and achieve fertilization. This altered interaction may be related to modified molecular communication between frozen-thawed ram spermatozoa, seminal plasma, and the female tract. As such, this review aims to identify the biological processes which underpin sperm maturation and transport throughout the female reproductive tract to elucidate factors which may alter this natural process in cryopreserved ram spermatozoa. We also assess critical barriers to ram spermatozoa specific to the ovine cervix and the role of seminal plasma in mitigating these barriers. Transcriptomics is explored as a new approach to understand the sperm-cervix interaction. Recent studies have demonstrated that both spermatozoa and seminal plasma contain a complex profile of coding and non-coding RNAs. These molecular species have clear links with functional fertility, and mounting evidence suggests they may be altered by cryopreservation. Emerging in vitro cell culture models are also investigated as a "next step" in studying this interaction, utilizing transcriptomics to identify subtle changes in female tract gene expression in response to spermatozoa. The application of such models is proposed as an exciting opportunity to investigate the unique challenges faced by cryopreserved spermatozoa traversing the ovine cervix prior to fertilization.

Reproductive biology research down under: highlights from the Australian and New Zealand Annual Meeting of the Society for Reproductive Biology, 2021.

Against the backdrop of a global pandemic, the Society for Reproductive Biology (SRB) 2021 meeting reunited the Australian and New Zealand reproductive research community for the first time since 2019 and was the first virtual SRB meeting. Despite the recent global research disruptions, the conference revealed significant advancements in reproductive research, the importance of which span human health, agriculture, and conservation. A core theme was novel technologies, including the use of medical microrobots for therapeutic and sperm delivery, diagnostic hyperspectral imaging, and hydrogel condoms with potential beyond contraception. The importance of challenging the contraceptive status quo was further highlighted with innovations in gene therapies, non-hormonal female contraceptives, epigenetic semen analysis, and in applying evolutionary theory to suppress pest population reproduction. How best to support pregnancies, particularly in the context of global trends of increasing maternal age, was also discussed, with several promising therapies for improved outcomes in assisted reproductive technology, pre-eclampsia, and pre-term birth prevention. The unique insights gained via non-model species was another key focus and presented research emphasised the importance of studying diverse systems to understand fundamental aspects of reproductive biology and evolution. Finally, the meeting highlighted how to effectively translate reproductive research into policy and industry practice.

Obesity and Male Reproduction; Placing the Western Diet in Context.

There is mounting evidence that obesity has negative repercussions for reproductive physiology in males. Much of this evidence has accumulated from rodent studies employing diets high in fat and sugar ("high fat" or "western" diets). While excessive fats and carbohydrates have long been considered major determinants of diet induced obesity, a growing body of research suggests that the relationships between diet composition and obesity are more complex than originally thought, involving interactions between dietary macronutrients. However, rodent dietary models have yet to evolve to capture this, instead relying heavily on elevated levels of a single macronutrient. While this approach has highlighted important effects of obesity on male reproduction, it does not allow for interpretation of the complex, interacting effects of dietary protein, carbohydrate and fat. Further, the single nutrient approach limits the ability to draw conclusions about which diets best support reproductive function. Nutritional Geometry offers an alternative approach, assessing outcomes of interest over an extended range of dietary macronutrient compositions. This review explores the practical application of Nutritional Geometry to study the effects of dietary macronutrient balance on male reproduction, including experimental considerations specific to studies of diet and reproductive physiology. Finally, this review discusses the promising use of Nutritional Geometry in the development of evidence-based pre-conception nutritional guidance for men.

Liquid chromatography-tandem mass spectrometry reveals an active response to DNA damage in human spermatozoa.

OBJECTIVE: To investigate how endogenously elevated DNA fragmentation alters the human sperm proteome, and whether this fragmentation contributes to genomic deletions. DESIGN: Research study. SETTING: Commercial fertility clinic. PATIENT(S): Men with low (0%-4%, n = 7) or high (≥16%, n = 6) sperm DNA fragmentation, as assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Global sperm proteome, single-nucleotide polymorphism genotyping array. RESULT(S): A total of 78 significantly differentially abundant proteins (30 decreased, 48 increased) were observed in control vs. high DNA damage samples. DNA damage resulted in robust proteomic responses, including markers of oxidative stress and apoptosis, DNA damage repair proteins, and transcription/translation and protein turnover machinery. Several key sperm functional proteins were significantly decreased in ejaculates with high DNA damage. We were unable to substantiate a link between increased DNA fragmentation and genomic deletions in human spermatozoa. CONCLUSION(S): Developing human spermatozoa initiate an active transcriptional response to endogenous DNA damage, which manifests as alterations in the sperm proteome.

Mitigating the Effects of Oxidative Sperm DNA Damage.

Sperm DNA damage is correlated with reduced embryo development and increased miscarriage risk, reducing successful conception. Given its links with oxidative stress, antioxidants have been investigated as a potential treatment, yet results are conflicting. Importantly, individual antioxidants are not identical in composition, and some compounds may be more effective than others. We investigated the use of the polyphenol-rich, high-antioxidant-capacity fruit acai as a treatment for elevated sperm DNA fragmentation (>16%), measured by terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL). Following ≥ 74 days of treatment, we observed a significant decrease in sperm DNA fragmentation (-17.0% ± 2.5%) to 11.9 ± 1.7% (0-37%), with a 68.6% success rate (defined as post-treatment TUNEL < 16%). Post-treatment decreases in DNA fragmentation and success rates were not significantly impacted by low motility and/or concentration, or exceptionally high (> 25%) TUNEL. Treatment significantly reduced concentration in men with normal semen parameters, but 88% remained normal. Overall, successful treatment was not associated with age, semen parameters or TUNEL result at baseline. However, body mass index was significantly higher in nonresponders at baseline. This study provides evidence of a low-cost, effective treatment for elevated sperm DNA damage using acai.

Quantitative Proteomic Analysis of Seminal Plasma, Sperm Membrane Proteins, and Seminal Extracellular Vesicles Suggests Vesicular Mechanisms Aid in the Removal and Addition of Proteins to the Ram Sperm Membrane.

Quantitative proteomic studies are contributing greatly to the understanding of the spermatozoon through the provision of detailed information on the proteins spermatozoa acquire and shed in the acquisition of fertility. Extracellular vesicles (EVs) are thought to aid in the delivery of proteins to spermatozoa in the male reproductive tract. The aim of this study is to isolate, identify and quantify EV proteins isolated from ram seminal plasma. Ram sperm plasma membrane proteins are also isolated using nitrogen cavitation and identified to better understand the interplay of proteins between the sperm membrane and extracellular environment. The categorization of proteins enriched in the EV population according to their function revealed three main groupings: vesicle biogenesis, metabolism, and membrane adhesion and remodeling. The latter group contains many reproduction-specific proteins that show demonstrable links to sperm fertility. Many of these membrane-bound proteins show testicular expression and are shed from the sperm surface during epididymal maturation (e.g., testis expressed 101; TEX101 and lymphocyte Antigen 6 Family Member K; LY6K). Their association with seminal EVs suggests that EVs may not only deliver protein cargo to spermatozoa but also assist in the removal of proteins from the sperm membrane.

Sublethal sperm freezing damage: Manifestations and solutions.

Semen cryopreservation is an important tool for artificial breeding, species conservation and human reproductive medicine. However, sublethal freezing damage remains an important limitation of the cryopreservation process, inevitably leading to reduced fertility in vivo. This review explores several facets of sublethal freezing damage, touching on cryocapacitation, the generation of reactive oxygen species and alterations to sperm proteins, lipids and sugars. The effects of sublethal freezing damage on sperm performance in vivo are also discussed, examining fertile lifespan and interaction with female reproductive tract immune cells, mucus and oviductal cells. Finally, the cryoprotective potential of whole seminal plasma and individual proteins are explored.

Binder of Sperm Proteins protect ram spermatozoa from freeze-thaw damage.

Cryopreservation causes sub-lethal damage which limits the fertility of frozen thawed spermatozoa. Seminal plasma has been investigated as a cryoprotectant, but has yielded inconsistent results due to considerable variation in its constituents. Individual seminal plasma proteins offer an ideal alternative to whole seminal plasma, and several have been correlated with freezing success. Binder of Sperm Proteins (BSPs) are abundant ram seminal plasma proteins which have been suggested to have significant protective effects on ram spermatozoa during cold shock. This is in direct opposition to bull spermatozoa, where BSPs cause sperm deterioration during in vitro handling. We investigated the potential of BSP1 and BSP5 to prevent freezing associated damage to important functional parameters of ram spermatozoa. BSPs purified by size exclusion chromatography improved post thaw motility and penetration through artificial mucus. Highly purified BSP1 and BSP5, isolated by gelatin affinity and RP-HPLC, improved motility and membrane integrity, and reduced post thaw protein tyrosine phosphorylation. Exposure to BSP5 before freezing increased the amount of phosphatidylethanolamine on the sperm surface after thawing. Neither BSP1 nor BSP5 prevented freezing associated changes in membrane lipid disorder. These results suggest that BSPs may significantly improve freezing outcomes of ram spermatozoa.

Binder of Sperm Proteins 1 and 5 have contrasting effects on the capacitation of ram spermatozoa.

Binder of Sperm Proteins (BSPs) are the most abundant seminal plasma protein family in the ram and bull. They have been extensively studied in the bull but less is known about their function in ovine seminal plasma and current knowledge suggests that BSPs may have different effects in these two species. In the bull, they facilitate capacitation and destabilize the sperm membrane during in vitro handling, whereas in the ram, they appear to stabilize the sperm membrane and prevent cryopreservation-induced capacitation-like changes. Further investigation into the effects of BSPs on ram spermatozoa under capacitating conditions is required to further clarify their physiological roles in the ram. We investigated the effects of Binder of Sperm Proteins 1 and 5 on epididymal ram spermatozoa in conditions of low, moderate, and high cAMP. BSPs had minimal effects on sperm function in low-cAMP conditions, but caused significant changes under cAMP upregulation. BSP1 stabilized the membrane and qualitatively reduced protein tyrosine phosphorylation, but significantly increased cholesterol efflux and induced spontaneous acrosome reactions. BSP5 slightly increased spontaneous acrosome reactions and caused sperm necrosis. However, BSP5 had minimal effects on membrane lipid order and cholesterol efflux and did not inhibit protein tyrosine phosphorylation. These findings demonstrate that under maximal cAMP upregulation, BSP1 affected ram spermatozoa in a manner comparable to bull spermatozoa, while BSP5 did not.

Seminal plasma and cryopreservation alter ram sperm surface carbohydrates and interactions with neutrophils.

Spermatozoa deposited vaginally must navigate the physical, chemical and immune barriers of the cervix to reach the site of fertilisation. Characteristics that favour successful cervical transit remain largely unknown beyond the obvious factors of motility and viability. Epididymal and cryopreserved ram spermatozoa demonstrate poor cervical transit, for unknown reasons. We hypothesised that seminal plasma exposure and cryopreservation alter the surface sugars of these sperm populations and, consequently, their interaction with immune cells, both potential factors for successful cervical transit. The carbohydrate profiles of epididymal, ejaculated and frozen-thawed ram spermatozoa were assessed by flow cytometry and western blotting using lectins for galactose, sialic acid, N-acetylglucosamine and mannose. Seminal plasma exposure and cryopreservation caused significant changes to the relative amounts of surface sugars detected by flow cytometry and lectin blotting. Immune cell interaction was characterised using a neutrophil-binding assay. Seminal plasma acted as a robust protective mechanism, limiting binding of spermatozoa, whereas the media used for cryopreservation caused a significant disruption to opsonin-mediated binding. We were unable to demonstrate a link between changes to surface sugars and neutrophil susceptibility. Seminal plasma and cryopreservation clearly alter the sperm glycocalyx, as well as the interaction of spermatozoa with immune cells.

Proteomic Investigation of Ram Spermatozoa and the Proteins Conferred by Seminal Plasma.

Sperm proteomes have emerged for several species; however, the extent of species similarity is unknown. Sheep are an important agricultural species for which a comprehensive sperm proteome has not been produced. In addition, potential proteomic factors from seminal plasma that may contribute to improved fertility after cervical insemination are yet to be explored. Here we use liquid chromatography-tandem mass spectrometry to investigate the proteome of ejaculated ram spermatozoa, with quantitative comparison to epididymal spermatozoa. We also present a comparison to published proteomes of five other species. We identified 685 proteins in ejaculated ram spermatozoa, with the most abundant proteins involved in metabolic pathways. Only 5% of ram sperm proteins were not detected in other species, which suggest highly conserved structures and pathways. Of the proteins present in both epididymal and ejaculated ram spermatozoa, 7% were more abundant in ejaculated spermatozoa. Only two membrane-bound proteins were detected solely in ejaculated sperm lysates: liver enriched gene 1 (LEG1/C6orf58) and epidermal growth factor-like repeats and discoidin I-like domains 3 (EDIL3). This is the first evidence that despite its relatively complex proteomic composition, seminal plasma exposure leads to few novel proteins binding tightly to the ram sperm plasma membrane.