Under-nutrition reduces spermatogenic efficiency and sperm velocity, and increases sperm DNA damage in sexually mature male sheep

Improving semen quality of rams fed with ration containing protected maggot oil

The study aimed to to evaluate the effect of feeding protected maggot oil at different levels on the ram sperm quality. The study used 15 local rams with an age of approximately 10-12 months and an initial weight of 19.99 ± 3.97 kg. The feeding rate was 4% of body weight per day. Feed was given 3 times a day, specifically in the morning (08.00 WIB), afternoon (12.00 WIB) and evening (16.00 WIB). Water was provided ad libitum. This study used 3 treatments and 5 groups as replicates. The treatments used concentrates with different levels of protected maggot oil: P0(0% protected maggot oil (control)), P1(4% protected maggot oil), and P2(8% protected maggot oil). The variables measured were nutrient consumption, blood cholesterol levels, scrotal circumference, and sperm quality. Blood cholesterol and scrotal circumference measured at the end of the experimental diet. Semen samples were collected and analysed before and at the end of the experimental diet. The data obtained were analysed using ANOVA, with further testing using Duncan's test for significant differences. The results showed that there were no significant differences in the consumption of dry matter, crude protein, crude fiber, scrotal circumference, volume, colour, pH of semen, sperm concentration, live percentage, abnormal percentage, plasma membrane, and acrosome integrity of spermatozoa. There were significantly (p < 0.05) produced higher consumption of oleic and palmitic acids in 8% protected maggot oil compared to 4% treatments, the treatments containing 4% and 8% protected maggot oil produced significantly (p < 0.05) higher consumption of lauric and myristic acids, blood cholesterol levels, and sperm motility than the control. The result indicates that protected maggot oil up to 8% in the ram diet have positive effect on improving the microscopic quality of ram sperm, i.e. increased sperm motility.

Sperm chromatin: Evaluation, epigenetic signatures and relevance for embryo development and assisted reproductive technology outcomes

Sperm chromatin is distinct from somatic cell chromatin, as a result of extensive remodeling during the final stages of spermatogenesis. In this process, the majority of histones is replaced with protamines. The chromatin is consequently highly condensed and inert, which facilitates protection of the DNA. The sperm epigenomic landscape is shaped by histone retention, histone and protamine modification, DNA methylation, and RNAs. In recent years, sperm chromatin integrity and its epigenetic marks have been increasingly studied, and the constitution of sperm chromatin is steadily being uncovered. This growing body of research prompts assessment of the frequently overlooked involvement of sperm in fertility and embryonic development. Moreover, numerous endogenous and exogenous factors are known to affect sperm chromatin, which may in turn impact the reproductive success. Concerns have been raised about the effects of assisted reproductive technology (ART) on the sperm epigenome, embryonic development and offspring health. This review examines the structure and epigenetic signatures of sperm chromatin in the context of fertility and early embryonic development. Additionally, sperm chromatin evaluation and causes of aberrant integrity are outlined. Building on the knowledge discussed in the current review, future research should aim to elucidate the intricate relationship between all aspects of sperm chromatin and embryo development. This could lead to the uncovering of new targets for treating infertility, as well as the acquisition of much needed insights into the possible reciprocal association between ART and sperm chromatin integrity.

Paternal effects on fetal programming

Paternal programming is the concept that the environmental signals from the sire's experiences leading up to mating can alter semen and ultimately affect the phenotype of resulting offspring. Potential mechanisms carrying the paternal effects to offspring can be associated with epigenetic signatures (DNA methylation, histone modification and non-coding RNAs), oxidative stress, cytokines, and the seminal microbiome. Several opportunities exist for sperm/semen to be influenced during development; these opportunities are within the testicle, the epididymis, or accessory sex glands. Epigenetic signatures of sperm can be impacted during the pre-natal and pre-pubertal periods, during sexual maturity and with advancing sire age. Sperm are susceptible to alterations as dictated by their developmental stage at the time of the perturbation, and sperm and seminal plasma likely have both dependent and independent effects on offspring. Research using rodent models has revealed that many factors including over/under nutrition, dietary fat, protein, and ingredient composition (e.g., macro- or micronutrients), stress, exercise, and exposure to drugs, alcohol, and endocrine disruptors all elicit paternal programming responses that are evident in offspring phenotype. Research using livestock species has also revealed that sire age, fertility level, plane of nutrition, and heat stress can induce alterations in the epigenetic, oxidative stress, cytokine, and microbiome profiles of sperm and/or seminal plasma. In addition, recent findings in pigs, sheep, and cattle have indicated programming effects in blastocysts post-fertilization with some continuing into post-natal life of the offspring. Our research group is focused on understanding the effects of common management scenarios of plane of nutrition and growth rates in bulls and rams on mechanisms resulting in paternal programming and subsequent offspring outcomes. Understanding the implication of paternal programming is imperative as short-term feeding and management decisions have the potential to impact productivity and profitability of our herds for generations to come.

QTLs and Candidate Genes Associated with Semen Traits in Merino Sheep

Ram semen traits play a significant role in conception outcomes, which in turn may influence reproductive efficiency and the overall productivity and profitability of sheep enterprises. Since hundreds of ewes may be inseminated from a single ejaculate, it is important to evaluate semen quality prior to use in sheep breeding programs. Given that semen traits have been found to be heritable, genetic variation likely contributes to the variability observed in these traits. Identifying such genetic variants could provide novel insights into the molecular mechanisms underlying variability in semen traits. Therefore, this study aimed to identify quantitative trait loci (QTLs) associated with semen traits in Merino sheep. A genome-wide association study (GWAS) was undertaken using 4506 semen collection records from 246 Merino rams collected between January 2002 and May 2021. The R package RepeatABEL was used to perform a GWAS for semen volume, gross motility, concentration, and percent post-thaw motility. A total of 35 QTLs, located on 16 Ovis aries autosomes (OARs), were significantly associated with either of the four semen traits in this study. A total of 89, 95, 33, and 73 candidate genes were identified, via modified Bonferroni, within the QTLs significantly associated with volume, gross motility, concentration, and percent post-thaw motility, respectively. Among the candidate genes identified, SORD, SH2B1, and NT5E have been previously described to significantly influence spermatogenesis, spermatozoal motility, and high percent post-thaw motility, respectively. Several candidate genes identified could potentially influence ram semen traits based on existing evidence in the literature. As such, validation of these putative candidates may offer the potential to develop future strategies to improve sheep reproductive efficiency. Furthermore, Merino ram semen traits are lowly heritable (0.071-0.139), and thus may be improved by selective breeding.

Substitution of soyabean meal by faba bean improves body weight, sperm production and testosterone concentration in mature Queue Fine de l'Ouest rams

The current study aimed at investigating the effects of partial or total substitution of soybean meal with faba bean on reproductive parameters of Queue Fine de l'Ouest rams. Eighteen adult rams (49.8 ± 3.7 kg and 2.4 ± 1.5 years old) were divided into three homogenous groups. Rams received oat hay ad libitum and 3 types of concentrate (33 g/BW^0.75) where soybean meal was the main protein source (SBM diet, n = 6), partially (50%, SBMFB diet, n = 6) or totally (100% FB diet, n = 6) substituted in nitrogen basis by local faba bean. The volume of ejaculate, sperm concentration and sperm mortality rate were measured weekly by collecting semen using an artificial vagina. Serial blood samples were collected 30 days and 120 days after the beginning of the experiment in order to assess plasma testosterone concentrations. The results showed that hay intake was affected (P < 0.05) by the nature of the nitrogen source incorporated (1032.3 ± 12.2; 1026.8 ± 56.6 and 972.8 ± 39.05 g DM/d for SBM, FB and SBMFB respectively. The average live weight of the rams increased from 49.8 ± 0.4 (week 1) to 57.3 ± 0.9 kg (week 17) without effect of the diet. A positive effect of faba bean incorporation in the concentrate was observed on ejaculate volume, concentration and spermatozoa production. All these parameters were significantly higher in SBMFB and FB groups than in SBM group (P < 0.05). The protein source did not affect the percentage of dead spermatozoa and the total abnormalities which were similar for the three diets (38.7; 35.8 and 38.1% for SBM; SBMFB and FB, respectively). The mean testosterone concentration was higher (P < 0.05) in rams fed with faba bean (1.7 ± 0.7 to 1.9 ± 0.7 ng/ml for the SBMFB and the FB groups respectively) than in rams fed SBM diet (1.06 ± 0.5 ng/ml). It was concluded that the substitution of soybean meal by faba bean improved the reproductive performance and did not affect sperm quality in Queue Fine de l'Ouest rams.

Melatonin alleviated oxidative stress induced by energy restriction on sheep Leydig cells through Sirt1/Sod2 pathway

Energy balance is essential for normal reproduction of ram. However, the effect of energy restriction (ER) on reactive oxygen species (ROS) of sheep Leydig cells (LCs) and the rescuee methods are still unclear. To investigate the in vitro effect of melatonin on cellular ROS in fER-treated sheep LCs and explore the underlying mechanism, Hu sheep LCs were restricted energy using no serum culture medium and resaved with 10 ng/ml melatonin, respectively. The results showed that ER significantly increased MDA level, while decreased CAT, GHS-px expression and ΔΨm (p < 0.05). Meanwhile, ER decreased testosterone concentration and cell proliferation rate (p < 0.05). And the expression of testosterone synthesis-related enzymes was also down-regulated by ER (p < 0.05). Furthermore, we revealed that melatonin reversed the defective phenotypes in ER-treated LCs via Sirt1/Sod2 pathway. The interference of Sirt1 abolished the melatonin-mediated improvement of cellular ROS and testosterone secretion. Taken together, our study firstly indicated that melatonin could alleviate the excessive ROS accumulation and promote testosterone biosynthesis in ER-treated sheep LCs via the activation of Sirt1/Sod2 pathway.

Treatment of rams with melatonin implants in the non-breeding season improves post-thaw sperm progressive motility and DNA integrity

In the Merino ram, it is unclear whether cryopreserved sperm function and fertility is compromised when collected during the non-breeding season, when Merino ewes are seasonally anestrus. It was therefore investigated whether treatment with melatonin could improve sperm function or fertility when semen was collected during the period Merino ewes were seasonally anestrus. There were 16 Merino rams treated or not treated with melatonin implants during the non-breeding season of ewes (September). Ejaculates were collected before melatonin treatment (Week 0), during the period of melatonin release (Week 7) and subsequent breeding season (Week 23). In vitro sperm function was assessed before freezing, and at 0- and 3 -hs post-thaw. Fertility was determined through intrauterine insemination of ewes (n = 966) with frozen-thawed samples, during the breeding season. Compared to Week 0 values, spermatozoa from melatonin-treated rams had greater progressive motility at Week 7 (P = 0.019) and less DNA fragmentation (P = 0.003) at Weeks 7 and 23, whilst spermatozoa from non-treated rams were unchanged during these time-periods. There were no other treatment effects on sperm function or fertility (P > 0.05). In ejaculates collected during Week 23, there were no effects of treatment either before freezing or post-thawing. Sperm from ejaculates collected at Week 23, however, had lesser pre-freezing/post-thawing total motility and resulted in lower pregnancy rates (P < 0.05). It is concluded there are no effects of season on sperm quality or fertility of Merino rams and that melatonin treatment subtly improves quality of spermatozoa following cryopreservation.

Individual variation in fresh and frozen semen of Bali bulls (Bos sondaicus)

AIM

This study aimed to analyze the individual factors influencing the sperm quality of Bali bulls at Baturiti Artificial Insemination (AI) center.

MATERIALS AND METHODS

Semen that was ejaculated from nine Bali bulls was collected using artificial vaginas (n=5/bull). Semen ejaculates were evaluated immediately after collection to measure the quality of the fresh semen, including semen volume, sperm concentration, progressive motility, membrane integrity (MI), and abnormal morphology. Frozen semen was evaluated for progressive sperm motility, concentration, viability, MI, abnormal morphology, and deoxyribonucleic acid (DNA) fragmentation. Other secondary data, focusing on semen quantity (semen volume and sperm concentration), were also collected from frozen the semen production data of the Baturiti AI center from 2017 to 2019. Data were analyzed statistically using a completely randomized design, and one-way analysis of variance was applied to find differences among individual bulls.

RESULTS

Significant differences (p<0.05) were found among the bulls in semen volume, sperm motility, concentration, and MI of the fresh semen. Significant differences (p<0.05) were also found among the bulls in sperm motility, viability, MI, abnormal morphology, and DNA fragmentation of the frozen semen.

CONCLUSION

Individual variation in all the tested sperm parameters of the fresh semen of Bali bulls, except sperm viability and abnormalities, was noted. Similarly, individual variation in all the tested sperm parameters in frozen semen, except sperm concentration, was noted. Therefore, individual factors can be used for selecting a superior bull in Bali cattle.

Maternal stress in sheep during late pregnancy influences sperm quality in early puberty of the offspring

Stress at the end of sheep gestation can damage the reproductive development of young males. The aim of the present study was to evaluate the effects of LPS administration in the last third of sheep pregnancy on the reproductive parameters of prepubertal rams. Thirty-six pregnant nulliparous ewes (12 ± 2 months old; 45 ± 6 kg) were assigned to two treatments, LPS (E. coli; 0.8 μg kg^-1) and control (placebo/saline) administered in late pregnancy (120 days post-conception). The animals gave birth to 17 male lambs (11 LPS; 8 control). Reproductive development of the young rams was analyzed from 5 to 12 months of age. A completely randomized design in double factorial scheme was used. The data were analyzed by analysis of variance. The model included treatment (LPS; control), age as main effects and their interactions, and the animal as a repeated measure. Means were compared by the PDIFF-SAS (Pr > |t|) at P < 0.05. An effect of age was observed for scrotal circumference, testicular consistency, homogeneity of testicular parenchyma, vascularization, semen quantity and quality, and blood testosterone concentration (P < 0.05). LPS increased sperm defects (P < 0.05) but an interaction with age was not observed (P > 0.05) with higher abnormalities only during months 8 and 9 (P < 0.05) and not thereafter. In summary, LPS did not cause long-term damage to testicular morphology analyzed from the onset of puberty to sexual maturity. However, LPS treatment affected sperm morphology during early puberty of the offspring.

High-energy diet enhances spermatogenic function and increases sperm midpiece length in fallow deer (Dama dama) yearlings

Nutrition is a major factor involved in the sexual development of livestock ruminants. In the male, a high-energy diet enhances the reproductive function, but its effects on the underlying processes such as spermatogenic efficiency are not yet defined. Moreover, the possible changes in sperm size due to a supplemented diet remain poorly investigated. The main goal of this study was to evaluate whether a high-energy diet affects the spermatogenic activity, epididymal sperm parameters (concentration, morphology, morphometry and acrosome integrity) and blood testosterone levels in fallow deer yearlings. For this purpose, 32 fallow deer were allocated into two groups according to their diet: control (pasture) and experimental (pasture and barley grain) groups. Fallow deer from the experimental group showed a significant increase in the Sertoli cell function and sperm midpiece length, together with a higher testicular mass, sperm concentration and percentage of normal spermatozoa than the control group (p < 0.05). We also found a tendency for higher blood testosterone levels in the animals fed with barley grain (p = 0.116). The better sperm quality found in the experimental group may be related to their higher efficiency of Sertoli cells and to an earlier onset of puberty. The results of the present work elucidate the mechanisms by which dietary supplementation enhances the male sexual development and might be useful for better practices of livestock management in seasonal breeders.

Improved early postnatal nutrition and its effect on histomorphological parameters in the testes of Sanjabi ram lambs

The effect of an ad libitum supplementary feeding on some reproductive characteristics of ram lambs were evaluated. Twelve Sanjabi rams were allocated to one of two groups: control (C) and treatment (T). The control group received hay and the treatment group received hay and concentrate with gross energy and crude protein concentration of 4.52 Mcal and 16% of dry matter, respectively. At the end of experiment, after taking blood samples for determination of testosterone concentration (TC), all lambs were castrated and the testicular weight (TWT), testicular volume (TV), testicular length (TL), and testicular width (TW) were measured. In addition, testes were subjected to histological analysis. Body weight (BW), TC, TWT, TL, and TV in the T group were higher (P < 0.05) than the C group. However, TW was not affected by diet (P > 0.05). Animals from the C group presented lower numbers (P < 0.05) of Sertoli (SCN), germ (GCN), and Leydig cell numbers (LCN) compared to the T group. Also, seminiferous tubule diameter (STD) in the T group was significantly greater than (P < 0.05) the C group. TWT had a significant association with TC (P < 0.05), STD (P < 0.01), SCN (P < 0.01), GCN (P < 0.05), and LCN (P < 0.05). TC was correlated with STD (P < 0.01), SCN (P < 0.01), GCN (P < 0.05), and LCN (P < 0.05). STD showed close correlation with SCN (P < 0.01), GCN (P < 0.01), and LCN (P < 0.05). Also, SCN had a positive association with GCN (P < 0.01) and LCN (P < 0.05). A positive correlation was found between GCN and LCN (P < 0.01). In conclusion, the plane of nutrition of growing ram lambs enhances their growth and testicular development and probably will increases their postpubertal reproductive performance.

Influences of different dietary energy level on sheep testicular development associated with AMPK/ULK1/autophagy pathway

Energy balance is an important feature for spermatozoa production in the testis. The 5'-AMP-activated protein kinase (AMPK) is a sensor of cell energy, has been implicated as a mediator between gonadal function and energy balance. Herein, we intended to determine the physiological effects of AMPK on testicular development in feed energy restricted and compensated pre-pubertal rams. Lambs had restricted feeding for 2 months and then provided compensatory feeding for another 3 months. Feed levels were 100%(control), 15% and 30% of energy restriction (ER) diets, respectively. The results showed that lambs fed the 30% ER diet had significantly lower testicular weight (P < .05) and spermatids number in the seminiferous tubules, but there were no differences between control and 15% ER groups. Meanwhile, 15% ER and 30% ER diets induced testis autophagy and apoptosis through activating AMPK-ULK1(ULK1, Unc-51 like autophagy activating kinase) signal pathway with characterization of increased Beclin-1 and Light chain 3-Ⅱ/Light chain 3-Ⅰ (LC3-II/LC3-I) ratio, up-regulated the ratio of pro-apoptotic Bcl-2-associated X protein (BAX) and anti-apoptotic B-cell lymphoma 2 (Bcl-2), as well as activated AMPK, phosphorylated AMPK(p-AMPK) and ULK1. Furthermore, a compensation of these parameters occurred when the lambs were re-fed with normal energy requirement after restriction. Taken together, dietary energy levels influence testicular development through autophagy and apoptosis interplay mediated by AMPK-ULK1 signal pathway, which also indicates the important role of the actions of AMPK in the testis homeostasis.

Cellular and molecular responses of adult testis to changes in nutrition: novel insights from the sheep model

This review explores the cellular and molecular mechanisms that regulate spermatogenesis in the post-pubertal testis that is regressing in response to mild undernutrition, using the sexually mature male sheep as a model. Testis regression leads to reductions in daily sperm production and in the quality of ejaculated spermatozoa (poorer movement, DNA damage). There is also a reduction in spermatogenic efficiency that appears to be caused, at least partially, by increases in germ cell apoptosis. Sertoli cell number does not change with testis regression, although about 1% of Sertoli cells do appear to retain proliferative ability after puberty. On the other hand, Sertoli cell function is disrupted during testis regression, as evidenced by a disorganization of tight junctions and indications that cell differentiation and maturation are reversed. Disrupted Sertoli cell function can explain, at least partially, the increase in germ cell apoptosis and any decrease in the rate of spermatogenesis, the two major contributors to spermatogenic efficiency. These outcomes seem to be mediated by changes in two RNA-based processes: (i) the expression of small non-coding RNAs that are involved in the regulation of Sertoli cell function, spermatogenesis and germ cell apoptosis and (ii) alternative pre-mRNA splicing that affects the regulation of spermatogenesis but does not appear to affect germ cell apoptosis, at least during testis progression induced by undernutrition in the male sheep. These research outcomes can be extended to other animal models and are relevant to issues in human male fertility.

Characterization of GALNTL5 gene sequence and expression in ovine testes and sperm

The polypeptide N-acetylgalactosaminyltransferase-like protein 5 (GALNTL5), which belongs to the polypeptide N-acetylgalactosaminyltransferase (pp-GalNAc-T) gene family, is a newly identified gene that is specifically expressed in testis and involved in spermatogenesis. However, there is no data showing the existence of GALNTL5 in ram testis at various developmental stages and its influence on sperm motility. Therefore, the objectives of the present study were to evaluate the presence of GALNTL5 in the testis of 3-24 months (M) ram and to investigate the expression of GALNTL5 in spermatozoa with different motilities. We detected a 1602 bp cDNA fragment of GALNTL5 that included a 1326 bp coding sequence, encoding 441 amino acids and 90 and 185 bp of the 5' and 3' untranslated regions, respectively. The GALNTL5 amino acid sequence showed 51.87-83.48% identity with the sequences of proteins from other species. It was detected exclusively in the testis and the levels of both the mRNA and protein were progressively increased with age. Immunohistochemistry further revealed that GALNTL5 specifically localized in the elongating spermatids and spermatozoa, and it was demonstrated to be strongly concentrated in the head, neck, and mid-piece region of spermatozoa by immunocytochemistry. The sperm density and the percentage of live sperm in the high motility group (≥80%) were significantly higher than in the low motility group (≤50%), and the reverse trend was observed with the abnormal sperm. Western blot analysis showed that the protein expression of PGK2, ALDOA, and GALNTL5 were significantly higher in the high motility group than in the low motility group. Overall, the data suggest that GALNTL5 is an important functional molecule during spermatogenesis. Moreover, it is the first to suggest that the expression level of GALNTL5 is positively correlated with the sperm motility.

Manchette-acrosome disorders during spermiogenesis and low efficiency of seminiferous tubules in hypercholesterolemic rabbit model

Hypercholesterolemia is a marker for several adult chronic diseases. Recently we demonstrated that sub/infertility is also associated to Hypercholesterolemia in rabbits. Seminal alterations included: abnormal sperm morphology, decreased sperm number and declined percentage of motile sperm, among others. In this work, our objective was to evaluate the effects of hypercholesterolemia on testicular efficiency and spermiogenesis, as the latter are directly related to sperm number and morphology respectively. Tubular efficiency was determined by comparing total number of spermatogenic cells with each cell type within the proliferation/differentiation compartments. We found lower testicular efficiency related to both a decrease in spermatogonial cells and an increase in germ cell apoptosis in hypercholesterolemic rabbits. On the other hand, spermiogenesis-the last step of spermatogenesis involved in sperm shaping-was detaily analyzed, particularly the acrosome-nucleus-manchette complex. The manchette is a microtubular-based temporary structure responsible in sperm cell elongation. We analyzed the contribution of actin filaments and raft microdomains in the arrangement of the manchette. Under fluorescence microscopy, spermatocyte to sperm cell development was followed in cells isolated from V to VIII tubular stages. In cells from hypercholesterolemic rabbits, abnormal development of acrosome, nucleus and inaccurate tail implantation were associated with actin-alpha-tubulin-GM1 sphingolipid altered distribution. Morphological alterations were also observed at electron microscopy. We demonstrated for the first time that GM1-enriched microdomains together with actin filaments and microtubules are involved in allowing the correct anchoring of the manchette complex. In conclusion, cholesterol enriched diets promote male fertility alterations by affecting critical steps in sperm development: spermatogenesis and spermiogenesis. It was also demonstrated that hypercholesterolemic rabbit model is a useful tool to study serum cholesterol increment linked to sub/infertility.

Functional changes in mRNA expression and alternative pre-mRNA splicing associated with the effects of nutrition on apoptosis and spermatogenesis in the adult testis

Background

The effects of nutrition on testis mass in the sexually mature male have long been known, however, the cellular and molecular processes of the testis response to nutrition was not fully understood.

Methods

We tested whether the defects in spermatogenesis and increases in germ cell apoptosis in the testis that are induced by under-nutrition are associated with changes in mRNA expression and pre-mRNA alternative splicing using groups of 8 male sheep fed for a 10% increase or 10% decrease in body mass over 65 days.

Results

We identified 2,243 mRNAs, including TP53 and Claudin 11, that were differentially expressed in testis from underfed and well-fed sheep (FDR < 0.1), and found that their expression changed in parallel with variations in germ cell numbers, testis size, and spermatogenesis. Furthermore, pairs of 269 mRNAs and 48 miRNAs were identified on the basis of target prediction. The regulatory effect of miRNAs on mRNA expression, in combination with functional analysis, suggests that these miRNAs are involved in abnormal reproductive morphology, apoptosis and male infertility. Nutrition did not affect the total number of alternative splicing events, but affected 206 alternative splicing events. A total of 159 genes, including CREM, SPATA6, and DDX4, were differentially spliced between dietary treatments, with functions related to RNA splicing and spermatogenesis. In addition, three gene modules were positively correlated with spermatogenesis-related phenotypic traits and negatively related to apoptosis-related phenotypic traits. Among these gene modules, seven (CFLAR, PTPRC, F2R, MAP3K1, EPHA7, APP, BCAP31) were also differentially expressed between nutritional treatments, indicating their potential as markers of spermatogenesis or apoptosis.

Conclusions

Our findings on significant changes in mRNAs and pre-mRNA alternative splicing under-nutrition suggest that they may partly explain the disruption of spermatogenesis and the increase germ cell apoptosis. However, more research is required to verify their causal effects in regulating spermatogenesis and germ cell apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3385-8) contains supplementary material, which is available to authorized users.

Roles of small RNAs in the effects of nutrition on apoptosis and spermatogenesis in the adult testis

We tested whether reductions in spermatozoal quality induced by under-nutrition are associated with increased germ cell apoptosis and disrupted spermatogenesis, and whether these effects are mediated by small RNAs. Groups of 8 male sheep were fed for a 10% increase or 10% decrease in body mass over 65 days. Underfeeding increased the number of apoptotic germ cells (P < 0.05) and increased the expression of apoptosis-related genes (P < 0.05) in testicular tissue. We identified 44 miRNAs and 35 putative piRNAs that were differentially expressed in well-fed and underfed males (FDR < 0.05). Some were related to reproductive system development, apoptosis (miRNAs), and sperm production and quality (piRNAs). Novel-miR-144 (miR-98), was found to target three apoptotic genes (TP53, CASP3, FASL). The proportion of miRNAs as a total of small RNAs was greater in well-fed males than in underfed males (P < 0.05) and was correlated (r = 0.8, P < 0.05) with the proportion of piRNAs in well-fed and underfed males. In conclusion, the reductions in spermatozoal quality induced by under-nutrition are caused, at least partly, by disruptions to Sertoli cell function and increased germ cell apoptosis, mediated by changes in the expression of miRNAs and piRNAs.

Nutrition affects Sertoli cell function but not Sertoli cell numbers in sexually mature male sheep

We tested whether the reversible effects of nutrition on spermatogenesis in sexually mature sheep were mediated by Sertoli cells. Rams were fed with diets designed to achieve a 10% increase (High), no change (Maintenance) or a 10% decrease (Low) in body mass after 65 days. At the end of treatment, testes were lighter in the Low than the High group (PP<0.05) in the expression of seven Sertoli cell-specific genes. Under-nutrition appeared to reverse cellular differentiation leading to disruption of tight-junction morphology. In conclusion, in sexually mature sheep, reversible reductions in testis mass and spermatogenesis caused by under-nutrition were associated with impairment of basic aspects of Sertoli cell function but not with changes in the number of Sertoli cells.